Iota

from Wikipedia:

Iota (uppercase Ι, lowercase ι; Greek: Ιώτα [iɔ̌ːta]) 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 this letter include the Roman and 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', meaning 'not the slightest amount', in reference to a phrase in the New Testament: "until heaven and earth pass away, not an iota, not a dot, will pass from the Law" (Mt 5:18).

The word 'jot' (or iot) derives from iota.

Symbol

The iota symbol is used to generate a vector of consecutive integers in the APL programming language.The name "iota" denotes 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 or is 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 superscript caret: .