ISO basic Latin alphabet
AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZz

I (named i /ˈaɪ/, plural ies)^[1] is the ninth letter and a vowel in the ISO basic Latin alphabet.

Egyptian hieroglyph ꜥ	Phoenician Yodh	Etruscan I	Greek Iota

In Semitic, the letter may have originated in a hieroglyph for an arm that represented a voiced pharyngeal fricative (/ʕ/) in Egyptian, but was reassigned to /j/ (as in English "yes") by Semites, because their word for "arm" began with that sound. This letter could also be used to represent /i/, the close front unrounded vowel, mainly in foreign words.

The Greeks adopted a form of this Phoenician yodh as their letter iota (⟨Ι, ι⟩) to represent /i/, the same as in the Old Italic alphabet. In Latin (as in Modern Greek), it was also used to represent /j/ and this use persists in the languages that descended from Latin. The modern letter 'j' was firstly a variation of 'i', and both were used interchangeably for both the vowel and the consonant, coming to be differentiated only in the 16th century. The dot over the lowercase 'i' is sometimes called a tittle. In the Turkish alphabet, dotted and dotless I are considered separate letters, representing a front and back vowel, respectively, and both have uppercase ('I', 'İ') and lowercase ('ı', 'i') forms.

In modern English, 'i' represents different sounds, either a "long" diphthong /aɪ/ as in kite, which developed from Middle English /iː/ after the Great Vowel Shift of the 15th century, or the "short" /ɪ/ as in bill.

The letter 'I' is the fifth most common letter in the English language. It is also used in mathematics to denote the imaginary unit

In some san serif typefaces, the uppercase letter I, 'I' may be difficult to distinguish from the lowercase letter L, 'l', the vertical bar character '|', or the digit one '1'. In serifed typefaces, the capital form of the letter has both a baseline and a cap-height serif, while the lowercase L has generally a hooked ascender and a baseline serif.

The uppercase I does not have a dot (tittle) while the lowercase i has it in the most of Latin-based alphabet schemes. However, some schemes, such as the Turkish alphabet, have two kinds of I's: the dotted one (İi) and the dotless one (Iı).

The uppercase I has two kinds of shapes, which are one with crossbars () and without crossbars (). Usually, they are considered same, but they are distinguished in some extended Latin alphabet system such as the 1978 version of the African reference alphabet. In the system, the former is the uppercase counterpart of ɪ and the latter is the counterpart of 'i'.

¹ Also for encodings based on ASCII, including the DOS, Windows, ISO-8859 and Macintosh families of encodings.

NATO phonetic	Morse code
India	▄ ▄ ⓘ

		File:Sign language .svg	File:BSL letter .svg
Signal flag	Flag semaphore	American manual alphabet (ASL fingerspelling)	British manual alphabet (BSL fingerspelling)	Braille dots-24 Unified English Braille

• Tittle
• Imaginary unit

• İ i and I ı : Latin dotted and dotless letter i
• І і : Cyrillic soft-dotted letter i
• И и : Cyrillic letter i

• Media related to I at Wikimedia Commons
• The dictionary definition of I at Wiktionary
• The dictionary definition of i at Wiktionary