Iota

Greek alphabet
Αα Alpha	Νν Nu
Ββ Beta	Ξξ Xi
Γγ Gamma	Οο Omicron
Δδ Delta	Ππ Pi
Εε Epsilon	Ρρ Rho
Ζζ Zeta	Σσς Sigma
Ηη Eta	Ττ Tau
Θθ Theta	Υυ Upsilon
Ιι Iota	Φφ Phi
Κκ Kappa	Χχ Chi
Λλ Lambda	Ψψ Psi
Μμ Mu	Ωω Omega
Obsolete letters
Digamma	Qoppa
San	Sampi
Other characters
Stigma	Sho
Heta
Greek diacritics

Iota (uppercase Ι, lowercase ι; Greek: Ιώτα [jɒta] Yota) 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 IPA: [/i/]. In ancient Greek it occurred in both long [i:] 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

Common English phrase

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 introduction to the Antithesis of the Law in the Gospel of Matthew (a jot or a tittle), and became common in the theological debate which caused the convening of the First Council of Nicaea, regarding the nature of the Holy Trinity. The argument centered on which of two alternative Greek words, differing only in a single 'iota' letter, should be used in describing Jesus' relationship to the Holy Trinity. One word, 'homoousios', would mean that Jesus was of the same substance as God the Father, and the other 'homoiousios', would mean that Jesus was of similar substance. This distinction separated the Arians, who believed the latter, from the main body of Christianity, and led to their ultimate condemnation as heretics.

Symbol

• The Iota symbol is used to generate a vector of consecutive integers in the APL 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.