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

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

 * , a common generic index variable often used in program loops
 * , an HTML element for marking italic type
 * , the common filename extension for a file that contains the output from a preprocessor
 * i-, a prefix for Apple products e.g. iMac, iPod, iPhone
 * 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

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
 * i (newspaper), a British newspaper based in London
 * 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 Toei Mita line symbol.svg
 * Imazatosuji Line, a subway service operated by the Osaka Metro, labeled Osaka Metro Imazatosuji line symbol.svg
 * JRW kinki-I.svg, 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