Iota

Iota (uppercase Ι, lowercase ι; Greek: Ιώτα [jɒta] Yota/Jota) is the ninth letter of the Greek alphabet. In the system of Greek numerals it has a value of 10. It was derived from the Phoenician letter Yodh (). Letters that arose from Iota include the Roman I and J and the Cyrillic І (І, і), Yi (Ї, ї), Je (Ј, ј), and iotified letters (e.g. Yu (Ю, ю)).

Iota represents [i]. In ancient Greek it occurred in both long [iː] and short [i] versions, but this distinction has been lost in Modern Greek.

Iota participated as the second element in falling diphthongs, 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 as iota subscript in other words as a very small ι under the main vowel, for instance ᾼ ᾳ ῌ ῃ ῼ ῳ

The word is used in a common English phrase, 'not one iota of difference', to signify a meaningless distinction (lit. "not even a small difference"). The phrase derives from the Arian controversy in the Christian community of the 4th century. Position accepted as orthodox at the First Council of Nicea was that the nature of Jesus of Nazareth (God the Son) was of the "same substance" (homoousios, ὁμοούσιος) as God the Father. By contrast, the followers of priest Arius maintained that he was not of the same subtance, but rather that he was either (1) of like(ὅμοιος, hómoios) substance as the Father in some subordinate sense of the term, or (2) of similar nature (without reference to substance) or of (3) unlike substance. While initially the one iota of a difference actually made a tremendous difference (ὁμοούσιος v ὁμοιούσιος, ie "of the same substance" v "of the like substance") eventually homoiousianist Arianists merged with orthodox homoousianists in opposition to other Christological views, in the process giving birth to the present-day saying.

Symbol

• The Iota symbol is used to generate a vector of consecutive integers in the APL programming language.
• The name "iota" is denoting a pseudo-constant to represent successive integers in the Go programming language.
• The lowercase Iota symbol is sometimes used to write the imaginary unit but more often Roman i or j are used.
• In logic, the lowercase iota denotes the definite descriptor.
• In mathematics and statistics, a unit vector is often denoted by a lowercase Iota letter with a superscribed caret: ${\hat {\imath }}$.