Iota (uppercase Ι, lowercase ι; Greek: Ιώτα [jota] Yota/Jota) 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 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', meaning 'not the slightest difference', 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.
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