1. Also called imaginary unit. the imaginary number .

  2. a unit vector on the x-axis of a coordinate system.

Words Nearby i

Other definitions for I (2 of 9)


or i

[ ahy ]

noun,plural I's or Is, i's or is.
  1. the ninth letter of the English alphabet, a vowel.

  2. any spoken sound represented by the letter I or i, as in big, nice, or ski.

  1. something having the shape of an I.

  2. a written or printed representation of the letter I or i.

  3. a device, as a printer's type, for reproducing the letter I ori.

Other definitions for I (3 of 9)

[ ahy ]

pronoun,nominative I,possessive my or mine,objective me;plural nominative we,possessive our or ours,objective us.
  1. the nominative singular pronoun, used in referring to oneself, the person speaking, writing, or otherwise communicating.

noun,plural I's.
  1. (used to denote the narrator of a literary work written in the first person singular.)

  2. Metaphysics. the ego.

Origin of I

First recorded before 900; Middle English ik, ich, i, Old English ic, ih; cognate with Gothic ik, German ich, Old Norse ek, Latin ego, Greek egṓ, Old Church Slavonic azŭ, Lithuanian aš, Sanskrit ahám

Grammar notes for I

See me.

Words that may be confused with I

Other definitions for I (4 of 9)


  1. interstate (used with a number to designate an interstate highway): I-95.

Other definitions for I (5 of 9)


  1. the ninth in order or in a series.

  2. (sometimes lowercase) the Roman numeral for 1.: Compare Roman numerals.

  1. Chemistry. iodine.

  2. Biochemistry. isoleucine.

  3. Electricity. current (def. 13).

  4. (italics)Physics. isotopic spin.

Other definitions for i- (6 of 9)


  1. variant of y-.

Other definitions for -i- (7 of 9)


  1. the typical ending of the first element of compounds of Latin words, as -o- is of Greek words, but often used in English with a first element of any origin, if the second element is of Latin origin: cuneiform; Frenchify.

Other definitions for i. (8 of 9)


  1. imperator.

  2. incisor.

  1. interest.

  2. intransitive.

  3. island.

  4. isle; isles.

Other definitions for I. (9 of 9)


  1. Independent.

  2. Island; Islands.

  1. Isle; Isles.

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2024

How to use i in a sentence

British Dictionary definitions for i (1 of 7)


symbol for
  1. the imaginary number √–1: Also called: j

British Dictionary definitions for i (2 of 7)



/ () /

nounplural i's, I's or Is
  1. the ninth letter and third vowel of the modern English alphabet

  2. any of several speech sounds represented by this letter, in English as in bite or hit

    • something shaped like an I

    • (in combination): an I-beam

  1. dot the i's and cross the t's to pay meticulous attention to detail

British Dictionary definitions for I (3 of 7)


/ () /

  1. (subjective) refers to the speaker or writer

Origin of I

C12: reduced form of Old English ic; compare Old Saxon ik, Old High German ih, Sanskrit ahám

British Dictionary definitions for I (4 of 7)


symbol for
  1. chem iodine

  2. physics current

  1. physics isospin

  2. logic a particular affirmative categorial statement, such as some men are married, often symbolized as SiP: Compare A, E, O 1

  3. (Roman numeral) one: See Roman numerals

abbreviation for
  1. Italy (international car registration)

Origin of I

(for sense 4) from Latin (aff) i (rmo) I affirm

British Dictionary definitions for -i- (5 of 7)


connective vowel
  1. used between elements in a compound word: cuneiform; coniferous Compare -o-

Origin of -i-

from Latin, stem vowel of nouns and adjectives in combination

British Dictionary definitions for -i (6 of 7)


suffix forming adjectives
  1. of or relating to a region or people, esp of the Middle East: Iraqi; Bangladeshi

Origin of -i

from an adjectival suffix in Semitic and in Indo-Iranian languages

British Dictionary definitions for I. (7 of 7)


abbreviation for
  1. International

  2. Island or Isle

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for i (1 of 2)


[ ī ]

  1. The number whose square is equal to -1. Numbers expressed in terms of i are called imaginary or complex numbers.

Scientific definitions for I (2 of 2)


  1. The symbol for electric current.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Other Idioms and Phrases with i


see dot the i's and cross the t's.

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.