Reference is a relationship between objects in which one object designates, or acts as a means by which to connect to or link to, another object. The first object in this relation is said to ''refer to'' the second object. It is called a ''

name A name is a term used for identification by an external observer. They can identify a class or category of things, or a single thing, either uniquely, or within a given context. The entity identified by a name is called its referent. A personal ...

'' for the second object. The second object, the one to which the first object refers, is called the ''

referent A referent () is a person or thing to which a name – a linguistic expression or other symbol – refers. For example, in the sentence ''Mary saw me'', the referent of the word ''Mary'' is the particular person called Mary who is being spoken of, ...

'' of the first object. A name is usually a

phrase In syntax and grammar, a phrase is a group of words or singular word acting as a grammatical unit. For instance, the English expression "the very happy squirrel" is a noun phrase which contains the adjective phrase "very happy". Phrases can consi ...

or expression, or some other symbolic representation. Its referent may be anything – a material object, a person, an event, an activity, or an abstract concept. References can take on many forms, including: a thought, a sensory perception that is

audible Audible may refer to: * Audible (service), an online audiobook store * Audible (American football), a tactic used by quarterbacks * ''Audible'' (film), a short documentary film featuring a deaf high school football player * Audible finish or rush ...

(

onomatopoeia Onomatopoeia is the process of creating a word that phonetically imitates, resembles, or suggests the sound that it describes. Such a word itself is also called an onomatopoeia. Common onomatopoeias include animal noises such as ''oink'', ''m ...

visual The visual system comprises the sensory organ (the eye) and parts of the central nervous system (the retina containing photoreceptor cells, the optic nerve, the optic tract and the visual cortex) which gives organisms the sense of sight (the ...

(text),

olfactory The sense of smell, or olfaction, is the special sense through which smells (or odors) are perceived. The sense of smell has many functions, including detecting desirable foods, hazards, and pheromones, and plays a role in taste. In humans, it ...

, or tactile,

emotional state Emotions are mental states brought on by neurophysiological changes, variously associated with thoughts, feelings, behavioral responses, and a degree of pleasure or displeasure. There is currently no scientific consensus on a definition. E ...

, relationship with other,

spacetime In physics, spacetime is a mathematical model that combines the three dimensions of space and one dimension of time into a single four-dimensional manifold. Spacetime diagrams can be used to visualize relativistic effects, such as why differen ...

coordinate,

symbolic Symbolic may refer to: * Symbol, something that represents an idea, a process, or a physical entity Mathematics, logic, and computing * Symbolic computation, a scientific area concerned with computing with mathematical formulas * Symbolic dynamic ...

or alpha-numeric, a physical object or an energy projection. In some cases, methods are used that intentionally hide the reference from some observers, as in

cryptography Cryptography, or cryptology (from grc, , translit=kryptós "hidden, secret"; and ''graphein'', "to write", or ''-logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of adver ...

. References feature in many spheres of human activity and knowledge, and the term adopts shades of meaning particular to the contexts in which it is used. Some of them are described in the sections below.

Etymology and meanings

The word ''reference'' is derived from

Middle English Middle English (abbreviated to ME) is a form of the English language that was spoken after the Norman conquest of 1066, until the late 15th century. The English language underwent distinct variations and developments following the Old English p ...

', from

Middle French Middle French (french: moyen français) is a historical division of the French language that covers the period from the 14th to the 16th century. It is a period of transition during which: * the French language became clearly distinguished from t ...

''référer'', from

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

''referre'', "to carry back", formed from the

prefix A prefix is an affix which is placed before the Word stem, stem of a word. Adding it to the beginning of one word changes it into another word. For example, when the prefix ''un-'' is added to the word ''happy'', it creates the word ''unhappy'' ...

''re''- and ''ferre'', "to bear". A number of words derive from the same root, including ''refer'', ''

referee A referee is an official, in a variety of sports and competition, responsible for enforcing the rules of the sport, including sportsmanship decisions such as ejection. The official tasked with this job may be known by a variety of other titl ...

'', ''referential'', ''

'', ''

referendum A referendum (plural: referendums or less commonly referenda) is a direct vote by the electorate on a proposal, law, or political issue. This is in contrast to an issue being voted on by a representative. This may result in the adoption of a ...

''. The verb ''refer (to)'' and its derivatives may carry the sense of "connect to" or "link to", as in the meanings of ''reference'' described in this article. Another sense is "consult"; this is reflected in such expressions as

reference work A reference work is a work, such as a paper, book or periodical (or their electronic equivalents), to which one can refer for information. The information is intended to be found quickly when needed. Such works are usually ''referred'' to f ...

reference desk The reference desk or information desk of a library is a public service counter where professional librarians provide library users with direction to library materials, advice on library collections and services, and expertise on multiple kinds ...

job reference A letter of recommendation or recommendation letter, also known as a letter of reference, reference letter or simply reference, is a document in which the writer assesses the qualities, characteristics, and capabilities of the person being recommen ...

, etc.

Semantics

semantics Semantics (from grc, σημαντικός ''sēmantikós'', "significant") is the study of reference, meaning, or truth. The term can be used to refer to subfields of several distinct disciplines, including philosophy Philosophy (f ...

, reference is generally construed as the relationships between

noun A noun () is a word that generally functions as the name of a specific object or set of objects, such as living creatures, places, actions, qualities, states of existence, or ideas.Example nouns for: * Living creatures (including people, alive, d ...

s or

pronoun In linguistics and grammar, a pronoun (abbreviated ) is a word or a group of words that one may substitute for a noun or noun phrase. Pronouns have traditionally been regarded as one of the parts of speech, but some modern theorists would not co ...

s and objects that are named by them. Hence, the

word A word is a basic element of language that carries an semantics, objective or pragmatics, practical semantics, meaning, can be used on its own, and is uninterruptible. Despite the fact that language speakers often have an intuitive grasp of w ...

"John" refers to the person John. The word "it" refers to some previously specified object. The object referred to is called the ''

'' of the word. Sometimes the word-object relation is called "

denotation In linguistics and philosophy, the denotation of an expression is its literal meaning. For instance, the English word "warm" denotes the property of being warm. Denotation is contrasted with other aspects of meaning including connotation. For inst ...

"; the word denotes the object. The converse relation, the relation from object to word, is called "

exemplification Exemplification, in the philosophy of language, is a mode of symbolization characterized by the relation between a sample and what it refers to. Description Unlike ostension, which is the act of showing or pointing to a sample, exemplification i ...

"; the object exemplifies what the word denotes. In syntactic analysis, if a word refers to a previous word, the previous word is called the " antecedent".

Meaning

Gottlob Frege Friedrich Ludwig Gottlob Frege (; ; 8 November 1848 – 26 July 1925) was a German philosopher, logician, and mathematician. He was a mathematics professor at the University of Jena, and is understood by many to be the father of analytic phil ...

argued that reference cannot be treated as identical with meaning: "

Hesperus In Greek mythology, Hesperus (; grc, Ἕσπερος, Hésperos) is the Evening Star, the planet Venus in the evening. He is one of the ''Astra Planeta''. A son of the dawn goddess Eos (Roman Aurora), he is the half-brother of her other son, Pho ...

" (an ancient Greek name for the evening star) and "

Phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...

" (an ancient Greek name for the morning star) both refer to

Venus Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never fa ...

, but the astronomical fact that '"Hesperus" is "Phosphorus"' can still be informative, even if the "meanings" of "Hesperus" and "Phosphorus" are already known. This problem led Frege to distinguish between the

sense and reference In the philosophy of language, the distinction between sense and reference was an idea of the German philosopher and mathematician Gottlob Frege in 1892 (in his paper "On Sense and Reference"; German: "Über Sinn und Bedeutung"), reflecting the ...

of a word. Some cases seem to be too complicated to be classified within this framework; the acceptance of the notion of

secondary reference {{Unreferenced, date=July 2021 Secondary reference points to the representation as a necessary part in granting a meaning to a (part of a) sentence. In this approach, words that don't contribute to the representation are void; they can only pr ...

may be necessary to fill the gap. See also

Opaque context An opaque context or referentially opaque context is a linguistic context in which it is not always possible to substitute "co-referential" expressions (expressions referring to the same object) without altering the truth of sentences. The expres ...

Linguistic sign

The very concept of the

linguistic sign In semiotics, a sign is anything that communicates a meaning that is not the sign itself to the interpreter of the sign. The meaning can be intentional, as when a word is uttered with a specific meaning, or unintentional, as when a symptom is t ...

is the combination of content and expression, the former of which may refer entities in the world or refer more abstract concepts, e.g. thought. Certain parts of speech exist only to express reference, namely anaphora such as

s. The subset of reflexives expresses co-reference of two participants in a sentence. These could be the

agent Agent may refer to: Espionage, investigation, and law *, spies or intelligence officers * Law of agency, laws involving a person authorized to act on behalf of another ** Agent of record, a person with a contractual agreement with an insuranc ...

(actor) and patient (acted on), as in "The man washed himself", the theme and recipient, as in "I showed Mary to herself", or various other possible combinations.

Computer science

computer science Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to Applied science, practical discipli ...

reference Reference is a relationship between objects in which one object designates, or acts as a means by which to connect to or link to, another object. The first object in this relation is said to ''refer to'' the second object. It is called a ''name'' ...

s are

data type In computer science and computer programming, a data type (or simply type) is a set of possible values and a set of allowed operations on it. A data type tells the compiler or interpreter how the programmer intends to use the data. Most progra ...

s that refer to an object elsewhere in memory and are used to construct a wide variety of

data structure In computer science, a data structure is a data organization, management, and storage format that is usually chosen for efficient access to data. More precisely, a data structure is a collection of data values, the relationships among them, a ...

s, such as

linked list In computer science, a linked list is a linear collection of data elements whose order is not given by their physical placement in memory. Instead, each element points to the next. It is a data structure consisting of a collection of nodes whic ...

s. Generally, a reference is a value that enables a program to directly access the particular data item. Most

programming language A programming language is a system of notation for writing computer programs. Most programming languages are text-based formal languages, but they may also be graphical. They are a kind of computer language. The description of a programming ...

s support some form of reference. For the specific type of reference used in the

C++ C++ (pronounced "C plus plus") is a high-level general-purpose programming language created by Danish computer scientist Bjarne Stroustrup as an extension of the C programming language, or "C with Classes". The language has expanded significan ...

language, see

reference (C++) A reference is a relationship between objects in which one object designates, or acts as a means by which to connect to or link to, another object. The first object in this relation is said to ''refer to'' the second object. It is called a ''name' ...

. The notion of reference is also important in relational

database theory Database theory encapsulates a broad range of topics related to the study and research of the theoretical realm of databases and database management systems. Theoretical aspects of data management include, among other areas, the foundations of q ...

; see

referential integrity Referential integrity is a property of data stating that all its references are valid. In the context of relational databases, it requires that if a value of one attribute (column) of a relation (table) references a value of another attribute (ei ...

Library and information sciences

References to many types of printed matter may come in an electronic or machine-readable form. For books, there exists the

ISBN The International Standard Book Number (ISBN) is a numeric commercial book identifier that is intended to be unique. Publishers purchase ISBNs from an affiliate of the International ISBN Agency. An ISBN is assigned to each separate edition and ...

and for journal articles, the Digital object identifier (DOI) is gaining relevance. Information on the

Internet The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, pub ...

may be referred to by a Uniform Resource Identifier (URI).

Psychology

In terms of mental processing, a

self-reference Self-reference occurs in natural or formal languages when a sentence, idea or formula refers to itself. The reference may be expressed either directly—through some intermediate sentence or formula—or by means of some encoding. In philoso ...

is used in psychology to establish identification with a mental state during self-analysis. This seeks to allow the individual to develop own frames of reference in a greater state of immediate awareness. However, it can also lead to circular reasoning, preventing evolution of thought. According to Perceptual Control Theory (PCT), a reference condition is the state toward which a control system's output tends to alter a controlled quantity. The main proposition is that "All behavior is oriented all of the time around the control of certain quantities with respect to specific reference conditions."

Scholarship

In academics and scholarship, a reference or bibliographical reference is a piece of information provided in a

footnote A note is a string of text placed at the bottom of a page in a book or document or at the end of a chapter, volume, or the whole text. The note can provide an author's comments on the main text or citations of a reference work in support of the ...

bibliography Bibliography (from and ), as a discipline, is traditionally the academic study of books as physical, cultural objects; in this sense, it is also known as bibliology (from ). English author and bibliographer John Carter describes ''bibliography ...

of a

written work Writing is a medium of human communication which involves the representation of a language through a system of physically inscribed, mechanically transferred, or digitally represented symbols. Writing systems do not themselves constitute ...

such as a book, article, essay, report, oration or any other

text Text may refer to: Written word * Text (literary theory), any object that can be read, including: **Religious text, a writing that a religious tradition considers to be sacred **Text, a verse or passage from scripture used in expository preachin ...

type, specifying the written work of another person used in the creation of that text. A bibliographical reference mostly includes the full name of the

author An author is the writer of a book, article, play, mostly written work. A broader definition of the word "author" states: "''An author is "the person who originated or gave existence to anything" and whose authorship determines responsibility f ...

, the title of their work and the year of publication. The primary purpose of references is to allow readers to examine the sources of a text, either for

validity Validity or Valid may refer to: Science/mathematics/statistics: * Validity (logic), a property of a logical argument * Scientific: ** Internal validity, the validity of causal inferences within scientific studies, usually based on experiments ** ...

or to learn more about the subject. Such items are often listed at the end of a work in a section marked ''References'' or ''Bibliography''. References are particularly important as for the use of

citation A citation is a reference to a source. More precisely, a citation is an abbreviated alphanumeric expression embedded in the body of an intellectual work that denotes an entry in the bibliographic references section of the work for the purpose of ...

s, since

copying Copying is the duplication of information or an artifact based on an instance of that information or artifact, and not using the process that originally generated it. With analog forms of information, copying is only possible to a limited degree o ...

of material by another author without proper reference and / or without required permissions is considered

plagiarism Plagiarism is the fraudulent representation of another person's language, thoughts, ideas, or expressions as one's own original work.From the 1995 '' Random House Compact Unabridged Dictionary'': use or close imitation of the language and thought ...

, and may be tantamount to

copyright infringement Copyright infringement (at times referred to as piracy) is the use of works protected by copyright without permission for a usage where such permission is required, thereby infringing certain exclusive rights granted to the copyright holder, s ...

, which can be subject to

legal proceeding Legal proceeding is an activity that seeks to invoke the power of a tribunal in order to enforce a law. Although the term may be defined more broadly or more narrowly as circumstances require, it has been noted that " e term ''legal proceedings'' i ...

s. A ''reference'' section contains only those works indeed cited in the main text of a work. In contrast, a ''bibliographical'' section often contains works not cited by the author, but used as background reading or listed as potentially useful to the reader. Keeping a

diary A diary is a written or audiovisual record with discrete entries arranged by date reporting on what has happened over the course of a day or other period. Diaries have traditionally been handwritten but are now also often digital. A personal ...

allows an individual to use references for personal organization, whether or not anyone else understands the systems of reference used. However, scholars have studied methods of reference because of their key role in communication and co-operation between ''different'' people, and also because of misunderstandings that can arise. Modern academic study of bibliographical references has been developing since the 19th century.

Law

patent A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an enabling disclosure of the invention."A p ...

law, a reference is a document that can be used to show the state of knowledge at a given time and that therefore may make a claimed

invention An invention is a unique or novel device, method, composition, idea or process. An invention may be an improvement upon a machine, product, or process for increasing efficiency or lowering cost. It may also be an entirely new concept. If an i ...

obvious or anticipated. Examples of references are patents of any country, magazine articles,

Ph.D. A Doctor of Philosophy (PhD, Ph.D., or DPhil; Latin: or ') is the most common degree at the highest academic level awarded following a course of study. PhDs are awarded for programs across the whole breadth of academic fields. Because it is a ...

theses that are indexed and thus accessible to those interested in finding information about the subject matter, and to some extent Internet material that is similarly accessible.

Arts

art Art is a diverse range of human activity, and resulting product, that involves creative or imaginative talent expressive of technical proficiency, beauty, emotional power, or conceptual ideas. There is no generally agreed definition of wha ...

, a reference is an item from which a work is based. This may include: * an existing artwork * a reproduction (i.e., a photo) * a directly observed object (e.g., a person) * the artist's memory Another example of reference is samples of various musical works being incorporated into a new one.

References

External links

Reference.com
– a multi-source encyclopedia search service, and language reference products provider *
References.net
– a directory of multidisciplinary reference resources on the web
Refmuseum.com
- The online museum of references {{logic Semantics Philosophical logic Concepts in logic Syntactic relationships Meaning (philosophy of language) Formal semantics (natural language)