# I (disambiguation)

I is the ninth letter of the Latin alphabet.
I or i may also refer to:

## Language

* I (pronoun), the first-person singular subject pronoun in English
* I (Cyrillic), a letter used in almost all ancient and modern Cyrillic alphabets
* ı, dotless I, letter used in Turkish and Azerbaijani
* i, close front unrounded vowel, in the International Phonetic Alphabet
* ɨ, close central unrounded vowel, in the International Phonetic Alphabet
* ɪ, near-close near-front unrounded vowel, in the International Phonetic Alphabet
* I (kana), one of the Japanese kana that each represent one mora
* I, male prefix to some Balinese names

## Science, technology, and mathematics
### Biology

* Troponin I, one of the three troponins
* Haplogroup I (mtDNA), a human mitochondrial DNA (mtDNA) haplogroup
* Haplogroup I (Y-DNA), a Y-chromosomal DNA (Y-DNA) haplogroup
* Olfactory nerve, the 1st cranial nerve in human anatomy
* the Lợn Ỉ or Vietnamese Pot-bellied pig

### Chemistry

* Iodine, symbol I, a chemical element
* I, isoleucine, an amino acid
* I, ionic strength in a chemical solution
* i, Van 't Hoff factor

### Computing

* i, a common generic index variable often used in program loops
* <i>, an HTML element for marking italic type
* .i, the common filename extension for a file that contains the output from a preprocessor
* i-, a prefix for Apple products and services e.g. iMac, iPod, iPhone, iCloud
* i-, an Internet-related prefix used by Internet and electronic companies

### Mathematics

* I, the Roman numeral for 1
* i, imaginary unit, for which i$^2$ = −1
* I or I$_n$, identity matrix of indeterminate size (or of size n)
* I, unit interval, which contains all real numbers from 0 to 1 inclusive
* i, an index variable, e. g. in a matrix or for summation
* I$_x$(a,b), the regularized incomplete beta function (of a variable x and parameters a,b)
* î, the unit vector along the x-axis in Cartesian coordinates

### Physics and astronomy

* I, i, electric current
* I, isospin
* I, luminous intensity
* I, moment of inertia
* i, orbital inclination
* I (Roman number one), in the Yerkes spectral classification scheme, the symbol for supergiants

### Telecommunication

* I band (NATO), the range of radio frequencies from 8 GHz to 10 GHz in the electromagnetic spectrum
* I, the ITU prefix allocated to Italy in radio communication
* I, in QAM modulation schemes, the in-phase communications channel

### Other uses in technology

* i, a suffix unit for video resolution (vertical Interlaced lines), as in 480i or 1080i
* I, in the YIQ colorspace commonly used with the NTSC television encoding scheme, the color-difference channel which is in-phase with the subcarrier

## Arts and media
### Music

* I (band), a Norwegian heavy metal band
* I, a diatonic function in tonal music theory

#### Albums

* i (A.R. Kane album), 1989
* I (Ben Lester album), 2019
* I (Cilvaringz album), 2007
* I (Cursed album), 2003
* I (Die Krupps album), 1992
* I (Felix Jaehn album), 2018
* I (Ikimono-gakari album), 2013
* I (Imminence album), 2014
* I (Jaejoong EP), 2013
* I (JonnyX and the Groadies album), 2005
* I (Juju album), 2018
* I (Kingston Wall album), 1992
* I (Kurt Nilsen album), 2003
* i (The Magnetic Fields album), 2004
* I (Meshuggah EP), 2004
* i (Misako Odani album), 1997
* I (Nightingale album), 2000
* I (Sahg album), 2006
* I (Taeyeon EP), 2015
* I (Xerath album), 2009
* I (soundtrack), by A. R. Rahman from the eponymous 2015 film

#### Songs

* "i" (Kendrick Lamar song), a 2014 song by Kendrick Lamar from his album To Pimp a Butterfly
* "i" (Lil Skies song), a song 2019 by Lil Skies from his debut album Shelby
* "I" (Taproot song), a 2001 song by band Taproot from their album Gift
* "I (Who Have Nothing)", a 1966 Ben. E. King song also recorded by Tom Jones, who used the title for one of his albums
* "I", a 2003 song on Weather Systems, an album by Andrew Bird
* "I", a 1992 song on Selected Ambient Works 85–92, an album by Aphex Twin
* "I", a 1992 song on Dehumanizer, an album by Black Sabbath
* "I", a 1997 song on Coal Chamber, an album by Coal Chamber
* "I", a 1967 song on Underground, an album by The Electric Prunes
* "I", a 2012 song on Muse, an album by Jolin Tsai
* "I", a 1981 song on Music from "The Elder", an album by Kiss
* "I", a 1994 song on Made in USA, an album by Pizzicato Five
* "I", a 1999 song on Eternal, an album by Samael
* "I", a 2003 song on Winter Story, an album by Shinhwa
* "I", a 2008 song on In the Shadow of a Thousand Suns, an album by Abigail Williams
* "I", a 2011 song on Cinderella's Eyes, an album by Nicola Roberts
* "I", a 2015 song on I, an EP by Taeyeon
* "I", a 2016 song by Rezz
* "I", a 2019 song by Hey! Say! JUMP

### Other media

* I (2015 film), an Indian Tamil-language film
* I (2016 film), an Iranian film
* i (TV network), the former name of ION Television
* The i Paper, a British newspaper, formerly known as i
* i (Portuguese newspaper), a Portuguese newspaper based in Lisbon
* I, a character in the comic book series Adventure into Fear
* "I" Is for Innocent, the ninth novel in Sue Grafton's "Alphabet mystery" series, published in 1992
* I, a Man, a 1967 Andy Warhol film

## Mythology

* Goddess I, a Mayan deity
* Hou-i, or I, a heroic archer and hunter in Chinese mythology

## Vehicles and transportation

* Italy (I), in the list of international vehicle registration codes
* Italy (aircraft registration prefix)
* Mitsubishi i, a Japanese kei car
* I (Los Angeles Railway), a former streetcar line in Los Angeles
* Toei Mita Line, a subway service operated by the Tokyo Metropolitan Bureau of Transportation (Toei), labeled
* Imazatosuji Line, a subway service operated by the Osaka Metro, labeled
* , the official West Japan Railway Company service symbol for the Kakogawa Line.

## Other uses

* i, an international symbol for visitor or tourist information; see ISO 7001
* Nintendo DSi, the third model in the Nintendo DS line, released in 2008
* Nintendo DSi XL, the larger version of the DSi, released in 2009
* I, an alternative romanization of Lee (Korean surname)
* I-Foundation, a charity in charge of state-funded Hindu faith schools in the United Kingdom
* Interest rate (i), in economics
* Investment (I), in economics
* India, the military time zone code for UTC+09:00