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The comma is a
punctuation Punctuation (or sometimes interpunction) is the use of spacing, conventional signs (called punctuation marks), and certain typographical devices as aids to the understanding and correct reading of written text, whether read silently or aloud. An ...
mark that appears in several variants in different languages. It has the same shape as an
apostrophe The apostrophe ( or ) is a punctuation mark, and sometimes a diacritical mark, in languages that use the Latin alphabet and some other alphabets. In English, the apostrophe is used for two basic purposes: * The marking of the omission of one o ...
or single closing
quotation mark Quotation marks (also known as quotes, quote marks, speech marks, inverted commas, or talking marks) are punctuation marks used in pairs in various writing systems to set off direct speech, a quotation, or a phrase. The pair consists of an ...
() in many
typeface A typeface (or font family) is the design of lettering that can include variations in size, weight (e.g. bold), slope (e.g. italic), width (e.g. condensed), and so on. Each of these variations of the typeface is a font. There are list of type ...
s, but it differs from them in being placed on the baseline of the text. Some typefaces render it as a small line, slightly curved or straight, but inclined from the vertical. Other fonts give it the appearance of a miniature filled-in figure on the baseline. The comma is used in many contexts and
language Language is a structured system of communication. The structure of a language is its grammar and the free components are its vocabulary. Languages are the primary means by which humans communicate, and may be conveyed through a variety of met ...
s, mainly to separate parts of a sentence such as
clause In language, a clause is a constituent that comprises a semantic predicand (expressed or not) and a semantic predicate. A typical clause consists of a subject and a syntactic predicate, the latter typically a verb phrase composed of a verb with ...
s, and items in lists mainly when there are three or more items listed. The word ''comma'' comes from the
Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...
(), which originally meant a cut-off piece, specifically in
grammar In linguistics, the grammar of a natural language is its set of structure, structural constraints on speakers' or writers' composition of clause (linguistics), clauses, phrases, and words. The term can also refer to the study of such constraint ...
, a short
clause In language, a clause is a constituent that comprises a semantic predicand (expressed or not) and a semantic predicate. A typical clause consists of a subject and a syntactic predicate, the latter typically a verb phrase composed of a verb with ...
. A comma-shaped mark is used as a
diacritic A diacritic (also diacritical mark, diacritical point, diacritical sign, or accent) is a glyph added to a letter or to a basic glyph. The term derives from the Ancient Greek (, "distinguishing"), from (, "to distinguish"). The word ''diacriti ...
in several writing systems and is considered distinct from the
cedilla A cedilla ( ; from Spanish) or cedille (from French , ) is a hook or tail ( ¸ ) added under certain letters as a diacritical mark to modify their pronunciation. In Catalan, French, and Portuguese (called cedilha) it is used only under the ' ...
. In
Byzantine The Byzantine Empire, also referred to as the Eastern Roman Empire or Byzantium, was the continuation of the Roman Empire primarily in its eastern provinces during Late Antiquity and the Middle Ages, when its capital city was Constantinopl ...
and modern copies of
Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic peri ...
, the "
rough Rough may refer to: * Roughness (disambiguation) * Rough (golf), the area outside the fairway on a golf course Geography * Rough (facility), former gas field now gas storage facility, off the Yorkshire coast of England People * Alan Rough (born 1 ...
" and "
smooth breathing The smooth breathing ( grc, ψιλὸν πνεῦμα, psilòn pneûma; ell, ψιλή ''psilí''; la, spīritus lēnis) is a diacritical mark used in polytonic orthography. In Ancient Greek, it marks the absence of the voiceless glottal frica ...
s" () appear above the letter. In Latvian,
Romanian Romanian may refer to: *anything of, from, or related to the country and nation of Romania **Romanians, an ethnic group **Romanian language, a Romance language ***Romanian dialects, variants of the Romanian language **Romanian cuisine, traditional ...
, and Livonian, the comma diacritic appears below the letter, as in . ''For the notation'' ''and'' /x/ ''used in this article, see
grapheme In linguistics, a grapheme is the smallest functional unit of a writing system. The word ''grapheme'' is derived and the suffix ''-eme'' by analogy with ''phoneme'' and other names of emic units. The study of graphemes is called ''graphemics' ...
and
phoneme In phonology and linguistics, a phoneme () is a unit of sound that can distinguish one word from another in a particular language. For example, in most dialects of English, with the notable exception of the West Midlands and the north-west o ...
, respectively.''


History

The development of
punctuation Punctuation (or sometimes interpunction) is the use of spacing, conventional signs (called punctuation marks), and certain typographical devices as aids to the understanding and correct reading of written text, whether read silently or aloud. An ...
is much more recent than the alphabet. In the 3rd century BC,
Aristophanes of Byzantium __NOTOC__ Aristophanes of Byzantium ( grc-gre, Ἀριστοφάνης ὁ Βυζάντιος ; BC) was a Hellenistic Greek scholar, critic and grammarian, particularly renowned for his work in Homeric scholarship, but also for work on other ...
invented a system of single
dots Directly observed treatment, short-course (DOTS, also known as TB-DOTS) is the name given to the tuberculosis (TB) control strategy recommended by the World Health Organization. According to WHO, "The most cost-effective way to stop the spread of T ...
() at varying levels, which separated verses and indicated the amount of breath needed to complete each fragment of the text when
reading Reading is the process of taking in the sense or meaning of Letter (alphabet), letters, symbols, etc., especially by Visual perception, sight or Somatosensory system, touch. For educators and researchers, reading is a multifaceted process invo ...
aloud. The different lengths were signified by a dot at the bottom, middle, or top of the line. For a short passage, a in the form of a dot was placed mid-level. This is the origin of the concept of a comma, although the name came to be used for the mark itself instead of the clause it separated. The mark used today is descended from a , a diagonal
slash Slash may refer to: * Slash (punctuation), the "/" character Arts and entertainment Fictional characters * Slash (Marvel Comics) * Slash (''Teenage Mutant Ninja Turtles'') Music * Harry Slash & The Slashtones, an American rock band * Nash ...
known as , used from the 13th to 17th centuries to represent a pause. The modern comma was first used by
Aldus Manutius Aldus Pius Manutius (; it, Aldo Pio Manuzio; 6 February 1515) was an Italian printer and humanist who founded the Aldine Press. Manutius devoted the later part of his life to publishing and disseminating rare texts. His interest in and preserv ...
.


Uses in English

In general, the comma shows that the words immediately before the comma are less closely or exclusively linked
grammatically In linguistics, the grammar of a natural language is its set of structural constraints on speakers' or writers' composition of clauses, phrases, and words. The term can also refer to the study of such constraints, a field that includes domains ...
to those immediately after the comma than they might be otherwise. The comma performs a number of functions in
English English usually refers to: * English language * English people English may also refer to: Peoples, culture, and language * ''English'', an adjective for something of, from, or related to England ** English national ide ...
writing. It is used in generally similar ways in other languages, particularly European ones, although the rules on comma usage – and their rigidity – vary from language to language.


The serial comma

Commas are placed between items in lists, as in ''They own a cat, a dog, two rabbits, and seven mice.'' Whether the final conjunction, most frequently ''and'', should be preceded by a comma, called the ''serial comma'', is one of the most disputed linguistic or stylistic questions in English. *They served apples, peaches, and bananas. (serial comma used) *We cleaned up cores, pits and skins. (serial comma omitted) The serial comma is used much more often, usually routinely, in the United States. A majority of American style guides mandate its use, including ''
The Chicago Manual of Style ''The Chicago Manual of Style'' (abbreviated in writing as ''CMOS'' or ''CMS'', or sometimes as ''Chicago'') is a style guide for American English published since 1906 by the University of Chicago Press. Its 17 editions have prescribed writi ...
'', Strunk and
White White is the lightest color and is achromatic (having no hue). It is the color of objects such as snow, chalk, and milk, and is the opposite of black. White objects fully reflect and scatter all the visible wavelengths of light. White on ...
's classic ''
The Elements of Style ''The Elements of Style'' is an American English writing style guide in numerous editions. The original was written by William Strunk Jr. in 1918, and published by Harcourt in 1920, comprising eight "elementary rules of usage", ten "elementary p ...
'', and the ''
U.S. Government Printing Office The United States Government Publishing Office (USGPO or GPO; formerly the United States Government Printing Office) is an agency of the legislative branch of the United States Federal government. The office produces and distributes information ...
Style Manual''. Conversely, the ''AP Stylebook'' for journalistic writing advises against it. The serial comma is also known as the Oxford comma, Harvard comma, or series comma. Although less common in British English, its usage occurs within both American and British English. It is called the Oxford comma because of its long history of use by Oxford University Press. According to ''New Hart's Rules'', "house style will dictate" whether to use the serial comma. "The general rule is that one style or the other should be used consistently." No association with region or dialect is suggested, other than that its use has been strongly advocated by Oxford University Press. Its use is preferred by Fowler's ''
Modern English Usage ''A Dictionary of Modern English Usage'' (1926), by Henry Watson Fowler (1858–1933), is a style guide to British English usage, pronunciation, and writing. Covering topics such as plurals and literary technique, distinctions among like words ...
''. It is recommended by the United States
Government Printing Office The United States Government Publishing Office (USGPO or GPO; formerly the United States Government Printing Office) is an agency of the legislative branch of the United States Federal government. The office produces and distributes information ...
,
Harvard University Press Harvard University Press (HUP) is a publishing house established on January 13, 1913, as a division of Harvard University, and focused on academic publishing. It is a member of the Association of American University Presses. After the retirem ...
, and the classic ''Elements of Style'' of
Strunk and White ''The Elements of Style'' is an American English writing style guide in numerous editions. The original was written by William Strunk Jr. in 1918, and published by Harcourt in 1920, comprising eight "elementary rules of usage", ten "elementary p ...
. Use of a comma may prevent ambiguity: * The sentence ''I spoke to the boys, Sam and Tom'' could mean either ''I spoke to the boys and Sam and Tom'' (I spoke to more than three people) or ''I spoke to the boys, who are Sam and Tom'' (I spoke to two people); * ''I spoke to the boys, Sam, and Tom'' – must be ''the boys and Sam and Tom'' (I spoke to more than three people). The serial comma does not eliminate all confusion. Consider the following sentence: *''I thank my mother, Anne Smith, and Thomas.'' This could mean either ''my mother and Anne Smith and Thomas'' (three people) or ''my mother, who is Anne Smith; and Thomas'' (two people). This sentence might be recast as "my mother (Anne Smith) and Thomas" for clarity. * ''I thank my mother, Anne Smith and Thomas.'' Because the comma after "mother" is conventionally used to prepare the reader for an apposite phrase – that is, a renaming of or further information about a noun – this construction suggests that my mother's name is "Anne Smith and Thomas". Compare "I thank my friend, Smith and Wesson", in which the ambiguity is obvious to those who recognise Smith and Wesson as a business name. As a
rule of thumb In English, the phrase ''rule of thumb'' refers to an approximate method for doing something, based on practical experience rather than theory. This usage of the phrase can be traced back to the 17th century and has been associated with various t ...
, ''
The Guardian ''The Guardian'' is a British daily newspaper. It was founded in 1821 as ''The Manchester Guardian'', and changed its name in 1959. Along with its sister papers ''The Observer'' and ''The Guardian Weekly'', ''The Guardian'' is part of the Gu ...
Style Guide'' suggests that straightforward lists (''he ate ham, eggs and chips'') do not need a comma before the final "and", but sometimes it can help the reader (''he ate cereal, kippers, bacon, eggs, toast and marmalade, and tea''). ''The Chicago Manual of Style'' and other academic writing guides require the serial comma: all lists must have a comma before the "and" prefacing the last item in a series . If the individual items of a list are long, complex, affixed with description, or themselves contain commas,
semicolon The semicolon or semi-colon is a symbol commonly used as orthographic punctuation. In the English language, a semicolon is most commonly used to link (in a single sentence) two independent clauses that are closely related in thought. When a ...
s may be preferred as separators, and the list may be introduced with a colon. In news headlines, a comma might replace the word "and", even if there are only two items, in order to save space, as in this headline from Reuters: * ''Trump, Macron engage in a little handshake diplomacy.''


Separation of clauses

Commas are often used to separate
clause In language, a clause is a constituent that comprises a semantic predicand (expressed or not) and a semantic predicate. A typical clause consists of a subject and a syntactic predicate, the latter typically a verb phrase composed of a verb with ...
s. In English, a comma is used to separate a
dependent clause A subordinate clause, dependent clause, subclause, or embedded clause is a clause that is embedded within a complex sentence. For instance, in the English sentence "I know that Bette is a dolphin", the clause "that Bette is a dolphin" occurs as t ...
from the
independent clause An independent clause (or main clause) is a clause that can stand by itself as a ''simple sentence''. An independent clause contains a subject and a predicate and makes sense by itself. Independent clauses can be joined by using a semicolon or ...
if the dependent clause comes first: ''After I fed the cat, I brushed my clothes.'' (Compare this with ''I brushed my clothes after I fed the cat.'') A
relative clause A relative clause is a clause that modifies a noun or noun phraseRodney D. Huddleston, Geoffrey K. Pullum, ''A Student's Introduction to English Grammar'', CUP 2005, p. 183ff. and uses some grammatical device to indicate that one of the arguments ...
takes commas if it is non-
restrictive In semantics, a modifier is said to be restrictive (or ''defining'') if it restricts the reference of its head. For example, in "the red car is fancier than the blue one", ''red'' and ''blue'' are restrictive, because they restrict which cars ''c ...
, as in ''I cut down all the trees, which were over six feet tall.'' (Without the comma, this would mean that only the trees more than six feet tall were cut down.) Some style guides prescribe that two
independent clause An independent clause (or main clause) is a clause that can stand by itself as a ''simple sentence''. An independent clause contains a subject and a predicate and makes sense by itself. Independent clauses can be joined by using a semicolon or ...
s joined by a coordinating
conjunction Conjunction may refer to: * Conjunction (grammar), a part of speech * Logical conjunction, a mathematical operator ** Conjunction introduction, a rule of inference of propositional logic * Conjunction (astronomy), in which two astronomical bodies ...
(''for'', ''and'', ''nor'', ''but'', ''or'', ''yet'', ''so'') must be separated by a comma placed before the conjunction. In the following sentences, where the second clause is independent (because it can stand alone as a sentence), the comma is considered by those guides to be necessary: * ''Mary walked to the party, but she was unable to walk home.'' * ''Designer clothes are silly, and I can't afford them anyway.'' * ''Don't push that button, or twelve tons of high explosives will go off right under our feet!'' In the following sentences, where the second half of the sentence is a dependent clause (because it does not contain an explicit subject), those guides prescribe that the comma be omitted: * ''Mary walked to the party but was unable to walk home.'' * ''I think designer clothes are silly and can't afford them anyway.'' However, such guides permit the comma to be omitted if the second independent clause is very short, typically when the second independent clause is an imperative, as in: * ''Sit down and shut up.'' The above guidance is not universally accepted or applied. Long
coordinate clause In grammar, a conjunction (abbreviated or ) is a part of speech that connects words, phrases, or clauses that are called the conjuncts of the conjunctions. That definition may overlap with that of other parts of speech and so what constitutes a ...
s are nonetheless usually separated by commas: * ''She had very little to live on, but she would never have dreamed of taking what was not hers.'' In some languages, such as
German German(s) may refer to: * Germany (of or related to) **Germania (historical use) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizens of Germany, see also German nationality law **Ger ...
and
Polish Polish may refer to: * Anything from or related to Poland, a country in Europe * Polish language * Poles, people from Poland or of Polish descent * Polish chicken *Polish brothers (Mark Polish and Michael Polish, born 1970), American twin screenwr ...
, stricter rules apply on comma use between clauses, with dependent clauses always being set off with commas, and commas being generally proscribed before certain coordinating conjunctions. The joining of two independent sentences with a comma and no conjunction (as in ''"It is nearly half past five, we cannot reach town before dark."'') is known as a ''
comma splice In written English usage, a comma splice or comma fault is the use of a comma to join two independent clauses. For example: The comma splice is sometimes used in literary writing to convey a particular mood of informality. In the United States i ...
'' and is sometimes considered an error in English; in most cases a semicolon should be used instead. A comma splice should not be confused, though, with the literary device called ''
asyndeton Asyndeton (, ; from the el, ἀσύνδετον, "unconnected", sometimes called asyndetism) is a literary scheme in which one or several conjunctions are deliberately omitted from a series of related clauses. Examples include ''veni, vidi, vici ...
'', in which coordinating conjunctions are purposely omitted for a specific stylistic effect. A much debated comma is the one in the
Second Amendment to the United States Constitution The Second Amendment (Amendment II) to the United States Constitution protects the Right to keep and bear arms in the United States, right to keep and bear arms. It was ratified on December 15, 1791, along with nine other articles of the Un ...
, which says ''"A well regulated Militia being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."'' but ratified by several states as ''"A well regulated Militia being necessary to the security of a free State, the right of the people to keep and bear Arms shall not be infringed."'' which has caused much debate on its interpretation.


Certain adverbs

Commas are always used to set off certain
adverb An adverb is a word or an expression that generally modifies a verb, adjective, another adverb, determiner, clause, preposition, or sentence. Adverbs typically express manner, place, time, frequency, degree, level of certainty, etc., answering ...
s at the beginning of a sentence, including ''however'', ''in fact'', ''therefore'', ''nevertheless'', ''moreover'', ''furthermore'', and ''still''. * ''Therefore, a comma would be appropriate in this sentence.'' * ''Nevertheless, I will not use one.'' If these adverbs appear in the middle of a sentence, they are followed and preceded by a comma. As in the second of the two examples below, if a semicolon separates the two sentences and the second sentence starts with an adverb, this adverb is preceded by a semicolon and followed by a comma. * ''In this sentence, furthermore, commas would also be called for.'' * ''This sentence is a bit different; however, a comma is necessary as well.'' Using commas to offset certain adverbs is optional, including ''then'', ''so'', ''yet'', ''instead'', and ''too'' (meaning ''also''). * ''So, that's it for this rule.'' or * ''So that's it for this rule.'' * ''A comma would be appropriate in this sentence, too.'' or * ''A comma would be appropriate in this sentence too.''


Parenthetical phrases

Commas are often used to enclose
parenthetical A bracket is either of two tall fore- or back-facing punctuation marks commonly used to isolate a segment of text or data from its surroundings. Typically deployed in symmetric pairs, an individual bracket may be identified as a 'left' or 'r ...
words and phrases within a sentence (i.e., information that is not essential to the meaning of the sentence). Such phrases are both preceded and followed by a comma, unless that would result in a doubling of punctuation marks or the parenthetical is at the start or end of the sentence. The following are examples of types of parenthetical phrases: *Introductory phrase: ''Once upon a time, my father ate a muffin.'' *Interjection: ''My father ate the muffin, gosh darn it!'' *Aside: ''My father, if you don't mind me telling you this, ate the muffin.'' *
Appositive Apposition is a grammatical construction in which two elements, normally noun phrases, are placed side by side so one element identifies the other in a different way. The two elements are said to be ''in apposition'', and one of the elements is c ...
: ''My father, a jaded and bitter man, ate the muffin.'' *Absolute phrase: ''My father, his eyes flashing with rage, ate the muffin.'' *Free modifier: ''My father, chewing with unbridled fury, ate the muffin.'' *Resumptive modifier: ''My father ate the muffin, a muffin which no man had yet chewed.'' *Summative modifier: ''My father ate the muffin, a feat which no man had attempted.'' The parenthesization of phrases may change the connotation, reducing or eliminating
ambiguity Ambiguity is the type of meaning in which a phrase, statement or resolution is not explicitly defined, making several interpretations plausible. A common aspect of ambiguity is uncertainty. It is thus an attribute of any idea or statement ...
. In the following example, the thing in the first sentence that is relaxing is the cool day, whereas in the second sentence it is the walk, since the introduction of commas makes "on a cool day" parenthetical: :''They took a walk on a cool day that was relaxing.'' :''They took a walk, on a cool day, that was relaxing.'' As more phrases are introduced, ambiguity accumulates, but when commas separate each phrase, the phrases clearly become modifiers of just one thing. In the second sentence below, that thing is ''the walk'': :''They took a walk in the park on a cool day that was relaxing.'' :''They took a walk, in the park, on a cool day, that was relaxing.''


Between adjectives

A comma is used to separate ''coordinate adjectives'' (i.e.,
adjectives In linguistics, an adjective (abbreviated ) is a word that generally modifies a noun or noun phrase or describes its referent. Its semantic role is to change information given by the noun. Traditionally, adjectives were considered one of the mai ...
that directly and equally modify the following noun). Adjectives are considered coordinate if the meaning would be the same if their order were reversed or if ''and'' were placed between them. For example: *''The dull, incessant droning'' but ''the cute little cottage.'' *''The devious lazy red frog'' suggests there are lazy red frogs (one of which is devious), while ''the devious, lazy red frog'' does not carry this connotation.


Before quotations

Some writers precede quoted material that is the grammatical object of an active verb of speaking or writing with a comma, as in ''Mr. Kershner says, "You should know how to use a comma."'' Quotations that follow and support an assertion are often preceded by a colon rather than a comma. Other writers do not put a comma before quotations unless one would occur anyway. Thus they would write ''Mr. Kershner says "You should know how to use a comma."''


In dates


Month day, year

When a date is written as a month followed by a day followed by a year, a comma separates the day from the year: December 19, 1941. This style is common in American English. The comma is used to avoid confusing consecutive numbers: December 19 1941. Most style manuals, including ''
The Chicago Manual of Style ''The Chicago Manual of Style'' (abbreviated in writing as ''CMOS'' or ''CMS'', or sometimes as ''Chicago'') is a style guide for American English published since 1906 by the University of Chicago Press. Its 17 editions have prescribed writi ...
'' and the ''
AP Stylebook The ''AP Stylebook'', also known by its full name ''The Associated Press Stylebook and Briefing on Media Law'', is an American English grammar style and usage guide created by American journalists working for or connected with the Associated Pr ...
'', also recommend that the year be treated as a parenthetical, requiring a second comma after it: ''"Feb. 14, 1987, was the target date."'' If just month and year are given, no commas are used: "Her daughter April may return in June 2009 for the reunion."


Day month year

When the day precedes the month, the month name separates the numeric day and year, so commas are not necessary to separate them: "The Raid on Alexandria was carried out on 19 December 1941."


In geographical names

Commas are used to separate parts of geographical references, such as city and state (''Dallas, Texas'') or city and country (''Kampala, Uganda''). Additionally, most style manuals, including ''
The Chicago Manual of Style ''The Chicago Manual of Style'' (abbreviated in writing as ''CMOS'' or ''CMS'', or sometimes as ''Chicago'') is a style guide for American English published since 1906 by the University of Chicago Press. Its 17 editions have prescribed writi ...
'' and the ''AP Stylebook'', recommend that the second element be treated as a parenthetical, requiring a second comma after: ''"The plane landed in Kampala, Uganda, that evening."'' The
United States Postal Service The United States Postal Service (USPS), also known as the Post Office, U.S. Mail, or Postal Service, is an independent agency of the executive branch of the United States federal government responsible for providing postal service in the U ...
and
Royal Mail , kw, Postya Riel, ga, An Post Ríoga , logo = Royal Mail.svg , logo_size = 250px , type = Public limited company , traded_as = , foundation = , founder = Henry VIII , location = London, England, UK , key_people = * Keith Williams ...
recommend leaving out punctuation when writing addresses on actual letters and packages, as the marks hinder
optical character recognition Optical character recognition or optical character reader (OCR) is the electronic or mechanical conversion of images of typed, handwritten or printed text into machine-encoded text, whether from a scanned document, a photo of a document, a scen ...
.
Canada Post Canada Post Corporation (french: Société canadienne des postes), trading as Canada Post (french: Postes Canada), is a Crown corporation that functions as the primary postal operator in Canada. Originally known as Royal Mail Canada (the opera ...
has similar guidelines, only making very limited use of hyphens.


In mathematics

Similar to the case in natural languages, commas are often used to delineate the boundary between multiple
mathematical object A mathematical object is an abstract concept arising in mathematics. In the usual language of mathematics, an ''object'' is anything that has been (or could be) formally defined, and with which one may do deductive reasoning and mathematical pr ...
s in a list (e.g., (3, 5, 12)). Commas are also used to indicate the
comma derivative In mathematics, the covariant derivative is a way of specifying a derivative along tangent vectors of a manifold. Alternatively, the covariant derivative is a way of introducing and working with a connection on a manifold by means of a different ...
of a
tensor In mathematics, a tensor is an algebraic object that describes a multilinear relationship between sets of algebraic objects related to a vector space. Tensors may map between different objects such as vectors, scalars, and even other tenso ...
.


In numbers

In representing large numbers, from the right side to the left, English texts usually use commas to separate each group of three digits in front of the decimal. This is almost always done for numbers of six or more digits, and often for four or five digits but not in front of the number itself. However, in much of Europe, Southern Africa and Latin America,
period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (or rhetorical period), a concept ...
s or spaces are used instead; the comma is used as a
decimal separator A decimal separator is a symbol used to separate the integer part from the fractional part of a number written in decimal form (e.g., "." in 12.45). Different countries officially designate different symbols for use as the separator. The cho ...
, equivalent to the use in English of the
decimal point A decimal separator is a symbol used to separate the integer part from the fractional part of a number written in decimal form (e.g., "." in 12.45). Different countries officially designate different symbols for use as the separator. The choi ...
. In India, the groups are two digits, except for the rightmost group, which is of three digits. In some styles, the comma may not be used for this purpose at all (e.g. in the SI writing style); a space may be used to separate groups of three digits instead.


In names

Commas are used when rewriting names to present the surname first, generally in instances of alphabetization by surname: ''Smith, John.'' They are also used before many titles that follow a name: ''John Smith, Ph.D.'' Similarly in lists that are presented with an inversion: ''...; socks, green: 3 pairs; socks, red: 2 pairs; tie, regimental: 1''.


Ellipsis

Commas may be used to indicate that a word, or a group of words, has been omitted, as in ''The cat was white; the dog, brown.'' (Here the comma replaces ''was''.)


Vocative

Commas are placed before, after, or around a noun or pronoun used independently in speaking to some person, place, or thing: *''I hope, John, that you will read this.''


Between the subject and predicate

In his 1785 essay ''An Essay on Punctuation'', Joseph Robertson advocated a comma between the subject and predicate of long sentences for clarity; however, this usage is regarded as an error in modern times. *''The good taste of the present age, has not allowed us to neglect the cultivation of the English language.'' *''Whoever is capable of forgetting a benefit, is an enemy to society.''


Differences between American and British usage in placement of commas and quotation marks

The comma and the
quotation mark Quotation marks (also known as quotes, quote marks, speech marks, inverted commas, or talking marks) are punctuation marks used in pairs in various writing systems to set off direct speech, a quotation, or a phrase. The pair consists of an ...
can be paired in several ways. In Great Britain and many other parts of the world, punctuation is usually placed within quotation marks only if it is part of what is being quoted or referred to: * My mother gave me the nickname "Bobby Bobby Bob Bob Boy", which really made me angry. In American English, the comma was commonly included inside a quotation mark: * My mother gave me the nickname "Bobby Bobby Bob Bob Boy," which really made me angry. However, this practice has fallen out of use in favor of the British form. During the
Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
, the British carried the comma over into abbreviations. Specifically, "Special Operations, Executive" was written "S.O.,E.". Nowadays, even the
full stop The full stop (Commonwealth English), period (North American English), or full point , is a punctuation mark. It is used for several purposes, most often to mark the end of a declarative sentence (as distinguished from a question or exclamation ...
s are frequently discarded.


Languages other than English


Western European languages

Western European languages like German, French, Italian, Spanish, and Portuguese use the same comma as English, with similar spacing, though usage may be somewhat different. For instance, in Standard German, subordinate clauses are always preceded by commas.


Comma variants

The basic comma is defined in Unicode as , and many variants by typography or language are also defined. : Some languages use a completely different sort of character for the purpose of the comma. : There are also a number of comma-like
diacritic A diacritic (also diacritical mark, diacritical point, diacritical sign, or accent) is a glyph added to a letter or to a basic glyph. The term derives from the Ancient Greek (, "distinguishing"), from (, "to distinguish"). The word ''diacriti ...
s with "" in their Unicode names that are not intended for use as
punctuation Punctuation (or sometimes interpunction) is the use of spacing, conventional signs (called punctuation marks), and certain typographical devices as aids to the understanding and correct reading of written text, whether read silently or aloud. An ...
. A comma-like low quotation mark is also available (shown below; corresponding sets of raised single quotation marks and double-quotation marks are not shown). : There are various other Unicode characters that include commas or comma-like figures with other characters or marks, that are not shown in these tables.


Languages other than Western European

Korean punctuation For the Korean language, South Korea mainly uses a combination of East Asian and European punctuation, while North Korea uses a little more of the East Asian punctuation style. Traditional Punctuation In the traditional Korean system of writin ...
uses both commas and
interpunct An interpunct , also known as an interpoint, middle dot, middot and centered dot or centred dot, is a punctuation mark consisting of a vertically centered dot used for interword separation in ancient Latin script. (Word-separating spaces did no ...
s for lists. In Unicode 5.2.0 "numbers with commas" ( through ) were added to the
Enclosed Alphanumeric Supplement Enclosed Alphanumeric Supplement is a Unicode block consisting of Latin alphabet characters and Arabic numerals enclosed in circles, ovals or boxes, used for a variety of purposes. It is encoded in the range U+1F100–U+1F1FF in the Supplem ...
block for compatibility with the
ARIB STD B24 character set Volume 1 of the Association of Radio Industries and Businesses (ARIB) STD-B24 standard for Broadcast Markup Language specifies, amongst other details, a character encoding for use in Japanese-language broadcasting. It was introduced on . The lates ...
.
Hebrew script The Hebrew alphabet ( he, אָלֶף־בֵּית עִבְרִי, ), known variously by scholars as the Ktav Ashuri, Jewish script, square script and block script, is an abjad script used in the writing of the Hebrew language and other Jewish ...
is also written from right to left. However,
Hebrew punctuation Hebrew punctuation is similar to that of English and other Western languages, Modern Hebrew having imported additional punctuation marks from these languages in order to avoid the ambiguities sometimes occasioned by the relative paucity of such ...
includes only a regular comma ().
Dravidian languages The Dravidian languages (or sometimes Dravidic) are a family of languages spoken by 250 million people, mainly in southern India, north-east Sri Lanka, and south-west Pakistan. Since the colonial era, there have been small but significant ...
such as
Tamil Tamil may refer to: * Tamils, an ethnic group native to India and some other parts of Asia **Sri Lankan Tamils, Tamil people native to Sri Lanka also called ilankai tamils **Tamil Malaysians, Tamil people native to Malaysia * Tamil language, nativ ...
,
Telugu Telugu may refer to: * Telugu language, a major Dravidian language of India *Telugu people, an ethno-linguistic group of India * Telugu script, used to write the Telugu language ** Telugu (Unicode block), a block of Telugu characters in Unicode S ...
,
Kannada Kannada (; ಕನ್ನಡ, ), originally romanised Canarese, is a Dravidian language spoken predominantly by the people of Karnataka in southwestern India, with minorities in all neighbouring states. It has around 47 million native s ...
, and
Malayalam Malayalam (; , ) is a Dravidian language spoken in the Indian state of Kerala and the union territories of Lakshadweep and Puducherry (Mahé district) by the Malayali people. It is one of 22 scheduled languages of India. Malayalam was des ...
also use the punctuation mark in similar usage to that of European languages with similar spacing. :ta:கால்புள்ளி (தமிழ் நடை)


Computing

In the common
character Character or Characters may refer to: Arts, entertainment, and media Literature * ''Character'' (novel), a 1936 Dutch novel by Ferdinand Bordewijk * ''Characters'' (Theophrastus), a classical Greek set of character sketches attributed to The ...
encoding systems
Unicode Unicode, formally The Unicode Standard,The formal version reference is is an information technology Technical standard, standard for the consistent character encoding, encoding, representation, and handling of Character (computing), text expre ...
and
ASCII ASCII ( ), abbreviated from American Standard Code for Information Interchange, is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment, and other devices. Because of ...
, character 44 ( 0x2C) corresponds to the comma symbol. The
HTML The HyperText Markup Language or HTML is the standard markup language for documents designed to be displayed in a web browser. It can be assisted by technologies such as Cascading Style Sheets (CSS) and scripting languages such as JavaScri ...
numeric character reference A numeric character reference (NCR) is a common markup construct used in SGML and SGML-derived markup languages such as HTML and XML. It consists of a short sequence of characters that, in turn, represents a single character. Since WebSgml, XML ...
is ,. In many computer languages commas are used as a field delimiter to separate arguments to a
function Function or functionality may refer to: Computing * Function key, a type of key on computer keyboards * Function model, a structured representation of processes in a system * Function object or functor or functionoid, a concept of object-oriente ...
, to separate elements in a
list A ''list'' is any set of items in a row. List or lists may also refer to: People * List (surname) Organizations * List College, an undergraduate division of the Jewish Theological Seminary of America * SC Germania List, German rugby union ...
, and to perform data designation on multiple variables at once. In the
C programming language ''The C Programming Language'' (sometimes termed ''K&R'', after its authors' initials) is a computer programming book written by Brian Kernighan and Dennis Ritchie, the latter of whom originally designed and implemented the language, as well as ...
the comma symbol is an operator which evaluates its first
argument An argument is a statement or group of statements called premises intended to determine the degree of truth or acceptability of another statement called conclusion. Arguments can be studied from three main perspectives: the logical, the dialectic ...
(which may have side-effects) and then returns the value of its evaluated second argument. This is useful in ''for'' statements and macros. In
Smalltalk Smalltalk is an object-oriented, dynamically typed reflective programming language. It was designed and created in part for educational use, specifically for constructionist learning, at the Learning Research Group (LRG) of Xerox PARC by Alan Ka ...
and APL, the
comma operator In the C and C++ programming languages, the comma operator (represented by the token ,) is a binary operator that evaluates its first operand and discards the result, and then evaluates the second operand and returns this value (and type); there ...
is used to
concatenate In formal language theory and computer programming, string concatenation is the operation of joining character strings end-to-end. For example, the concatenation of "snow" and "ball" is "snowball". In certain formalisations of concatenat ...
collections, including strings. In APL, it is also used monadically to rearrange the items of an array into a list. In
Prolog Prolog is a logic programming language associated with artificial intelligence and computational linguistics. Prolog has its roots in first-order logic, a formal logic, and unlike many other programming languages, Prolog is intended primarily ...
, the comma is used to denote
Logical Conjunction In logic, mathematics and linguistics, And (\wedge) is the truth-functional operator of logical conjunction; the ''and'' of a set of operands is true if and only if ''all'' of its operands are true. The logical connective that represents this ...
("and"). The
comma-separated values A comma-separated values (CSV) file is a delimited text file that uses a comma to separate values. Each line of the file is a data record. Each record consists of one or more fields, separated by commas. The use of the comma as a field separat ...
(CSV) format is very commonly used in exchanging text data between database and spreadsheet formats.


Diacritical usage

The comma is used as a
diacritic A diacritic (also diacritical mark, diacritical point, diacritical sign, or accent) is a glyph added to a letter or to a basic glyph. The term derives from the Ancient Greek (, "distinguishing"), from (, "to distinguish"). The word ''diacriti ...
mark in
Romanian Romanian may refer to: *anything of, from, or related to the country and nation of Romania **Romanians, an ethnic group **Romanian language, a Romance language ***Romanian dialects, variants of the Romanian language **Romanian cuisine, traditional ...
under (, ), and under (, ). A
cedilla A cedilla ( ; from Spanish) or cedille (from French , ) is a hook or tail ( ¸ ) added under certain letters as a diacritical mark to modify their pronunciation. In Catalan, French, and Portuguese (called cedilha) it is used only under the ' ...
is occasionally used instead of it, but this is technically incorrect. The symbol (' d with comma below') was used as part of the
Romanian transitional alphabet The Romanian transitional alphabet ( ro, Alfabetul român de tranziție), also known as the civil alphabet ( ro, alfabetul civil), was a series of alphabets containing a mix of Cyrillic and Latin script, Latin characters used for the Romanian la ...
(19th century) to indicate the sounds denoted by the Latin letter or letters , where derived from a Cyrillic ѕ (, ). The comma and the cedilla are both derivative of (a small cursive ) placed below the letter. From this standpoint alone, , , and could potentially be regarded as stand-ins for /sz/, /tz/, and /dz/ respectively. In Latvian, the comma is used on the letters , , , , and historically also , to indicate palatalization. Because the lowercase letter has a
descender In typography and handwriting, a descender is the portion of a letter that extends below the baseline of a font. For example, in the letter ''y'', the descender is the "tail", or that portion of the diagonal line which lies below the ''v'' c ...
, the comma is rotated 180° and placed over the letter. Although their
Adobe Adobe ( ; ) is a building material made from earth and organic materials. is Spanish for ''mudbrick''. In some English-speaking regions of Spanish heritage, such as the Southwestern United States, the term is used to refer to any kind of e ...
glyph A glyph () is any kind of purposeful mark. In typography, a glyph is "the specific shape, design, or representation of a character". It is a particular graphical representation, in a particular typeface, of an element of written language. A g ...
names are 'letter with comma', their names in the
Unicode Unicode, formally The Unicode Standard,The formal version reference is is an information technology Technical standard, standard for the consistent character encoding, encoding, representation, and handling of Character (computing), text expre ...
Standard are 'letter with a cedilla'. They were introduced to the Unicode standard before 1992 and, per Unicode Consortium policy, their names cannot be altered. In Livonian, whose alphabet is based on a mixture of Latvian and
Estonian Estonian may refer to: * Something of, from, or related to Estonia, a country in the Baltic region in northern Europe * Estonians, people from Estonia, or of Estonian descent * Estonian language * Estonian cuisine * Estonian culture See also

...
alphabets, the comma is used on the letters , , , , to indicate palatalization in the same fashion as Latvian, except that Livonian uses and to represent the same
palatal The palate () is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but in most other tetrapods, the oral and nasal cavities are not truly separ ...
plosive In phonetics, a plosive, also known as an occlusive or simply a stop, is a pulmonic consonant in which the vocal tract is blocked so that all airflow ceases. The occlusion may be made with the tongue tip or blade (, ), tongue body (, ), lips ...
phonemes which Latvian writes as and respectively. In
Czech Czech may refer to: * Anything from or related to the Czech Republic, a country in Europe ** Czech language ** Czechs, the people of the area ** Czech culture ** Czech cuisine * One of three mythical brothers, Lech, Czech, and Rus' Places *Czech, ...
and Slovak, the diacritic in the characters , , and resembles a superscript comma, but it is used instead of a
caron A caron (), háček or haček (, or ; plural ''háčeks'' or ''háčky'') also known as a hachek, wedge, check, kvačica, strešica, mäkčeň, varnelė, inverted circumflex, inverted hat, flying bird, inverted chevron, is a diacritic mark ( ...
because the letter has an ascender. Other ascender letters with carons, such as letters (used in
Finnish Romani Finnish Kalo () is a language of the Romani language, Romani language family (a subgroup of Indo-European languages, Indo-European) spoken by Finnish Kale. The language is related to but not mutually intelligible with Scandoromani language, Scand ...
and
Lakota Lakota may refer to: *Lakota people, a confederation of seven related Native American tribes *Lakota language, the language of the Lakota peoples Place names In the United States: *Lakota, Iowa *Lakota, North Dakota, seat of Nelson County *Lakota ...
) and (used in Skolt Sami), did not modify their carons to superscript commas. In 16th-century
Guatemala Guatemala ( ; ), officially the Republic of Guatemala ( es, República de Guatemala, links=no), is a country in Central America. It is bordered to the north and west by Mexico; to the northeast by Belize and the Caribbean; to the east by H ...
, the archaic letter
cuatrillo Cuatrillo (capital: Ꜭ, small: ꜭ) (Spanish for "little four") is a letter of several colonial Mayan alphabets in the Latin script that is based on the digit 4. It was invented by a Franciscan friar, Alonso de la Parra, in the 16th century to r ...
with a comma ( and ) was used to write Mayan languages.


See also

*
Hebrew cantillation Hebrew cantillation is the manner of chanting ritual readings from the Hebrew Bible in synagogue services. The chants are written and notated in accordance with the special signs or marks printed in the Masoretic Text of the Bible, to comple ...
*
Copy editing Copy editing (also known as copyediting and manuscript editing) is the process of revising written material ( copy) to improve readability and fitness, as well as ensuring that text is free of grammatical and factual errors. ''The Chicago Manual o ...
*
English punctuation English usually refers to: * English language * English people English may also refer to: Peoples, culture, and language * ''English'', an adjective for something of, from, or related to England ** English national ide ...
*
Latin-script alphabet A Latin-script alphabet (Latin alphabet or Roman alphabet) is an alphabet that uses letters of the Latin script. The 21-letter archaic Latin alphabet and the 23-letter classical Latin alphabet belong to the oldest of this group. The 26-letter ...
*
List of typographical symbols and punctuation marks Typographical symbols and punctuation marks are marks and symbols used in typography with a variety of purposes such as to help with legibility and accessibility, or to identify special cases. This list gives those most commonly encountered with L ...
*
Ogonek The (; Polish: , "little tail", diminutive of ) is a diacritic hook placed under the lower right corner of a vowel in the Latin alphabet used in several European languages, and directly under a vowel in several Native American languages. It i ...
*
Part of speech In grammar, a part of speech or part-of-speech (abbreviated as POS or PoS, also known as word class or grammatical category) is a category of words (or, more generally, of lexical items) that have similar grammatical properties. Words that are assi ...
*
Sentence clause structure In grammar, sentence and clause structure, commonly known as sentence composition, is the classification of sentences based on the number and kind of clauses in their syntactic structure. Such division is an element of traditional grammar. Typolo ...
*
Traditional grammar Traditional grammar (also known as classical grammar) is a framework for the description of the structure of a language. The roots of traditional grammar are in the work of classical Greek and Latin philologists. The formal study of grammar based ...


Related history

*
Global spread of the printing press The global spread of the printing press began with the invention of the printing press with movable type by Johannes Gutenberg in Mainz, Germany . Western printing technology was adopted in all world regions by the end of the 19th century, displ ...
*
History of printing in East Asia Printing in East Asia originated from the Han dynasty (220 BCE – 206 CE) in China, evolving from ink rubbings made on paper or cloth from texts on stone tables used during the Han. Printing is considered one of the Four Great Inventions of China ...
* History of sentence spacing *
History of Western typography Modern typographers view typography as a craft with a very long history tracing its origins back to the first punches and dies used to make seals and coinage currency in ancient times. The basic elements of typography are at least as old as ci ...


References


External links


''Grammar, Punctuation, and Capitalization'' – a comprehensive online guide by NASA
– a satirical suggestion to settle the problem of the Oxford Comma once and for all

– another satirical compromise between the American and British traditions relating to quotes and commas. {{Authority control Punctuation Greek-script diacritics Latin-script diacritics