Iota (; uppercase: Ι, lowercase: ι; ) is the ninth letter of the

Greek alphabet The Greek alphabet has been used to write the Greek language since the late 9th or early 8th century BCE. It is derived from the earlier Phoenician alphabet, and was the earliest known alphabetic script to have distinct letters for vowels as w ...

. It was derived from the Phoenician letter

Yodh Yodh (also spelled jodh, yod, or jod) is the tenth letter of the Semitic abjads, including Phoenician Yōd /𐤉, Hebrew Yōd , Aramaic Yod , Syriac Yōḏ ܝ, and Arabic . Its sound value is in all languages for which it is used; in many l ...

. Letters that arose from this letter include the

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 ...

I and J, the Cyrillic І (І, і), Yi (Ї, ї), and Je (Ј, ј), and iotated letters (e.g. Yu (Ю, ю)). In the system of

Greek numerals Greek numerals, also known as Ionic, Ionian, Milesian, or Alexandrian numerals, are a system of writing numbers using the letters of the Greek alphabet. In modern Greece, they are still used for ordinal numbers and in contexts similar to tho ...

, iota has a value of 10. Iota represents the

close front unrounded vowel The close front unrounded vowel, or high front unrounded vowel, is a type of vowel sound that occurs in most spoken languages, represented in the International Phonetic Alphabet by the symbol i. It is similar to the vowel sound in the English wo ...

. In early forms of ancient Greek, it occurred in both long and short versions, but this distinction was lost in

Koine Greek Koine Greek (; Koine el, ἡ κοινὴ διάλεκτος, hē koinè diálektos, the common dialect; ), also known as Hellenistic Greek, common Attic, the Alexandrian dialect, Biblical Greek or New Testament Greek, was the common supra-reg ...

. Iota participated as the second element in

falling diphthong A diphthong ( ; , ), also known as a gliding vowel, is a combination of two adjacent vowel sounds within the same syllable. Technically, a diphthong is a vowel with two different targets: that is, the tongue (and/or other parts of the speech ...

s, with both long and short vowels as the first element. Where the first element was long, the iota was lost in pronunciation at an early date, and was written in

polytonic orthography Greek orthography has used a variety of diacritics starting in the Hellenistic period. The more complex polytonic orthography ( el, πολυτονικό σύστημα γραφής, translit=polytonikó sýstīma grafī́s), which includes fi ...

iota subscript The iota subscript is a diacritic mark in the Greek alphabet shaped like a small vertical stroke or miniature iota placed below the letter. It can occur with the vowel letters eta , omega , and alpha . It represents the former presence of an o ...

, in other words as a very small ι under the main vowel. Examples include ᾼ ᾳ ῌ ῃ ῼ ῳ. The former diphthongs became digraphs for simple vowels in

.see

Koine Greek phonology The Greek language underwent pronunciation changes during the Koine Greek period, from about 300 BC to 400 AD. At the beginning of the period, the pronunciation was close to Classical Greek, while at the end it was almost identical to Modern Gree ...

The word is used in a common English phrase, "not one iota", meaning "not the slightest amount". This refers to iota, the smallest letter, or possibly

yodh Yodh (also spelled jodh, yod, or jod) is the tenth letter of the Semitic abjads, including Phoenician Yōd /𐤉, Hebrew Yōd , Aramaic Yod , Syriac Yōḏ ܝ, and Arabic . Its sound value is in all languages for which it is used; in many l ...

, י, the smallest letter in the Hebrew alphabet. The English word '' jot'' derives from iota. The German, Portuguese, and Spanish name for the letter J ('' Jot'' / '' jota'') is derived from iota.

Symbol

* In some

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 (e.g., A+, APL,

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 ...

, Go), iota (either as the lowercase symbol ⍳ or the identifier iota) is used to represent and generate an array of consecutive integers. For example, in APL ⍳4 gives 1 2 3 4. * The lowercase iota symbol is sometimes used to write the

imaginary unit The imaginary unit or unit imaginary number () is a solution to the quadratic equation x^2+1=0. Although there is no real number with this property, can be used to extend the real numbers to what are called complex numbers, using addition an ...

, but more often Roman i or j is used. * In mathematics, the

inclusion map In mathematics, if A is a subset of B, then the inclusion map (also inclusion function, insertion, or canonical injection) is the function \iota that sends each element x of A to x, treated as an element of B: \iota : A\rightarrow B, \qquad \iota ...

of one space into another is sometimes denoted by the lowercase iota. * In

logic Logic is the study of correct reasoning. It includes both formal and informal logic. Formal logic is the science of deductively valid inferences or of logical truths. It is a formal science investigating how conclusions follow from premise ...

, the lowercase iota denotes the definite descriptor. * The lowercase iota symbol has Unicode code point U+03B9 and the uppercase U+0399.

Character encodings

Greek Iota /
Ypogegrammeni The iota subscript is a diacritic mark in the Greek alphabet shaped like a small vertical stroke or miniature iota placed below the letter. It can occur with the vowel letters eta , omega , and alpha . It represents the former presence of an o ...

Coptic Iaude

Latin Iota Sample "ɩ" from various typefaces. Latin iota (majuscule: , minuscule: ɩ) is a letter of the Latin alphabet, based on the lowercase of the Greek letter iota (ι). It was formerly used in the International Phonetic Alphabet to represent (the ...

Cyrillic Iota

Technical Iota

Mathematical Iota

These characters are used only as mathematical symbols. Stylized Greek text should be encoded using the normal Greek letters, with markup and formatting to indicate text style.

References

{{Reflist Greek letters Vowel letters