Iota

This article is about Greek iota. For Latin iota, see ɩ. For Cyrillic Iota, see Iota (Cyrillic). For other uses, see Iota (disambiguation).

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 and the Cyrillic І (І, і), Yi (Ї, ї), Je (Ј, ј), and iotated letters (e.g. Yu (Ю, ю)).

In the system of Greek numerals iota has a value of 10.

Iota represents the sound [i]. In ancient Greek it occurred in both long [iː] and short [i] versions, but this distinction was lost in Koine 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 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.

Symbol

• In some programming languages (e.g. Go, APL, A+) iota (either its lowercase symbol ι or iota, as a keyword) is used to represent an array of consecutive integers. For example, in APL ι4 gives 1 2 3 4.
• The lowercase iota symbol is sometimes used to write the imaginary unit, but more often Roman i or j is used.
• In mathematics, the inclusion map of one space into another is sometimes denoted by the lowercase iota.
• In logic, the lowercase iota denotes the definite descriptor.
• The lowercase iota symbol has Unicode code point U+03B9 and the uppercase U+0399.

Character encodings

• Greek Iota / Ypogegrammeni

Character	Ι		ι		ᶥ		℩
Unicode name	GREEK CAPITAL LETTER IOTA		GREEK SMALL LETTER IOTA		MODIFIER LETTER SMALL IOTA		TURNED GREEK SMALL LETTER IOTA
Encodings	decimal	hex	decimal	hex	decimal	hex	decimal	hex
Unicode	921	U+0399	953	U+03B9	7589	U+1DA5	8489	U+2129
UTF-8	206 153	CE 99	206 185	CE B9	225 182 165	E1 B6 A5	226 132 169	E2 84 A9
Numeric character reference	Ι	Ι	ι	ι	ᶥ	ᶥ	℩	℩
Named character reference	Ι		ι
DOS Greek	136	88	160	A0
DOS Greek-2	173	AD	227	E3
Windows 1253	201	C9	233	E9
TeX			\iota

Character	ͺ		ͅ		ι
Unicode name	GREEK YPOGEGRAMMENI		COMBINING GREEK YPOGEGRAMMENI		GREEK PROSGEGRAMMENI
Encodings	decimal	hex	decimal	hex	decimal	hex
Unicode	890	U+037A	837	U+0345	8126	U+1FBE
UTF-8	205 186	CD BA	205 133	CD 85	225 190 190	E1 BE BE
Numeric character reference	ͺ	ͺ	ͅ	ͅ	ι	ι

• Coptic Iaude

Character	Ⲓ		ⲓ
Unicode name	COPTIC CAPITAL LETTER IAUDE		COPTIC SMALL LETTER IAUDE
Encodings	decimal	hex	decimal	hex
Unicode	11410	U+2C92	11411	U+2C93
UTF-8	226 178 146	E2 B2 92	226 178 147	E2 B2 93
Numeric character reference	Ⲓ	Ⲓ	ⲓ	ⲓ

• Latin Iota

Character	Ɩ		ɩ
Unicode name	LATIN CAPITAL LETTER IOTA		LATIN SMALL LETTER IOTA
Encodings	decimal	hex	decimal	hex
Unicode	406	U+0196	617	U+0269
UTF-8	198 150	C6 96	201 169	C9 A9
Numeric character reference	Ɩ	Ɩ	ɩ	ɩ

• Cyrillic Iota

Character	Ꙇ		ꙇ
Unicode name	CYRILLIC CAPITAL LETTER IOTA		CYRILLIC SMALL LETTER IOTA
Encodings	decimal	hex	decimal	hex
Unicode	42566	U+A646	42567	U+A647
UTF-8	234 153 134	EA 99 86	234 153 135	EA 99 87
Numeric character reference	Ꙇ	Ꙇ	ꙇ	ꙇ

• Technical Iota

Character	⍳		⍸
Unicode name	APL FUNCTIONAL SYMBOL IOTA		APL FUNCTIONAL SYMBOL IOTA UNDERBAR
Encodings	decimal	hex	decimal	hex
Unicode	9075	U+2373	9080	U+2378
UTF-8	226 141 179	E2 8D B3	226 141 184	E2 8D B8
Numeric character reference	⍳	⍳	⍸	⍸

• Mathematical Iota

Character	𝚰		𝛊		𝛪		𝜄		𝜤		𝜾
Unicode name	MATHEMATICAL BOLD CAPITAL IOTA		MATHEMATICAL BOLD SMALL IOTA		MATHEMATICAL ITALIC CAPITAL IOTA		MATHEMATICAL ITALIC SMALL IOTA		MATHEMATICAL BOLD ITALIC CAPITAL IOTA		MATHEMATICAL BOLD ITALIC SMALL IOTA
Encodings	decimal	hex	decimal	hex	decimal	hex	decimal	hex	decimal	hex	decimal	hex
Unicode	120496	U+1D6B0	120522	U+1D6CA	120554	U+1D6EA	120580	U+1D704	120612	U+1D724	120638	U+1D73E
UTF-8	240 157 154 176	F0 9D 9A B0	240 157 155 138	F0 9D 9B 8A	240 157 155 170	F0 9D 9B AA	240 157 156 132	F0 9D 9C 84	240 157 156 164	F0 9D 9C A4	240 157 156 190	F0 9D 9C BE
UTF-16	55349 57008	D835 DEB0	55349 57034	D835 DECA	55349 57066	D835 DEEA	55349 57092	D835 DF04	55349 57124	D835 DF24	55349 57150	D835 DF3E
Numeric character reference	𝚰	𝚰	𝛊	𝛊	𝛪	𝛪	𝜄	𝜄	𝜤	𝜤	𝜾	𝜾

Character	𝝞		𝝸		𝞘		𝞲
Unicode name	MATHEMATICAL SANS-SERIF BOLD CAPITAL IOTA		MATHEMATICAL SANS-SERIF BOLD SMALL IOTA		MATHEMATICAL SANS-SERIF BOLD ITALIC CAPITAL IOTA		MATHEMATICAL SANS-SERIF BOLD ITALIC SMALL IOTA
Encodings	decimal	hex	decimal	hex	decimal	hex	decimal	hex
Unicode	120670	U+1D75E	120696	U+1D778	120728	U+1D798	120754	U+1D7B2
UTF-8	240 157 157 158	F0 9D 9D 9E	240 157 157 184	F0 9D 9D B8	240 157 158 152	F0 9D 9E 98	240 157 158 178	F0 9D 9E B2
UTF-16	55349 57182	D835 DF5E	55349 57208	D835 DF78	55349 57240	D835 DF98	55349 57266	D835 DFB2
Numeric character reference	𝝞	𝝞	𝝸	𝝸	𝞘	𝞘	𝞲	𝞲

These characters are used only as mathematical symbols. Stylized Greek text should be encoded using the normal Greek letters, with markup and formatting to indicate text style.