Iota // (uppercase Ι, lowercase ι; Greek: ιώτα) is the ninth letter of the Greek alphabet. It was derived from the Phoenician letter Yodh. Letters that arose from this letter include the Latin I and J, the Cyrillic І (І, і), Yi (Ї, ї), and Je (Ј, ј), and iotated letters (e.g. Yu (Ю, ю)).
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. Examples include ᾼ ᾳ ῌ ῃ ῼ ῳ. The former diphthongs became digraphs for simple vowels in Koine Greek.
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 (Matthew 5:18): "until heaven and earth pass away, not an iota, not a dot, (King James Version: '[not] one jot or one tittle') will pass from the Law until all is accomplished". (Mt 5:18) This refers to iota, the smallest letter, or possibly Yodh, י, the smallest letter in the Hebrew alphabet.
The word 'jot' (or iot) derives from iota.
The German, Portuguese, and Spanish name for the letter J (Jot / jota) is derived from iota.
⍳or the identifier
iota) is used to represent and generate an array of consecutive integers. For example, in APL
1 2 3 4.