Merriam-Webster Logo
SINCE 1828
Menu
dictionary thesaurus
1

key

noun \ ˈkē \

Definition of key

1 a : a usually metal instrument by which the bolt of a lock is turned
b : any of various devices having the form or function of such a key
  • a key for winding a clock
2 a : a means of gaining or preventing entrance, possession, or control
b : an instrumental or deciding factor
  • the key to her success
3 a : something that gives an explanation or identification or provides a solution
  • the key to a riddle
b : a list of words or phrases giving an explanation of symbols or abbreviations
  • a pronunciation key in a dictionary
c : an aid to interpretation or identification : clue
  • a key to understanding their motivation
d : an arrangement of the salient characters of a group of plants or animals or of taxa designed to facilitate identification
e : a map legend
4 a : a part to be depressed by a finger that serves as one unit of a keyboard; also : a representation of such a key (such as a space delineated on a touch screen)
  • Tiny keys on your iPhone's screen can be difficult to hit accurately.
  • —Cherlynn Low
b : one of the levers of a keyboard musical instrument that actuates the mechanism and produces the tones
c : a lever that controls a vent in the side of a woodwind instrument or a valve in a brass instrument
5 : a system of tones and harmonies generated from a hierarchical scale of seven tones based on a tonic
  • the key of G major
6 a : characteristic style or tone
b : the tone or pitch of a voice
c : the predominant tone of a photograph with respect to its lightness or darkness
7 : a decoration or charm resembling a key
8 : a small switch for opening or closing an electric circuit
  • a telegraph key
9 : the set of instructions governing the encipherment and decipherment of messages
  • an encryption key
10 : a free-throw area in basketball : free throw lane
  • a jump shot from the top of the key
11 a (1) : cotter pin
(2) : cotter
b : a keystone in an arch
c : a small piece of wood or metal used as a wedge or for preventing motion between parts
12 : samara
—

keyed

play \ˈkēd\ adjective
—

keyless

play \ˈkē-ləs\ adjective

Origin and Etymology of key

Middle English, from Old English cǣg; akin to Old Frisian kēi key

Other Cartography Terms

Robinson projection, benchmark, plat, projection, topography

2

key

adjective

Definition of key

: extremely or crucially important
  • key issues
  • a key moment in the game
  • a key member of the staff

See key defined for English-language learners

Examples of key in a Sentence

  1. He's a key player in the organization.

  2. The key question is “Can we afford it?”.

  3. Underline key words and phrases as you read.

  4. Their votes were key in getting the bill passed.

Origin and Etymology of key

see 1key

key Synonyms

Synonyms

arch, big, capital, cardinal, central, chief, dominant, first, foremost, grand, great, greatest, highest, leading, main, master, overbearing, overriding, paramount, predominant, preeminent, premier, primal, primary, principal, prior, sovereign (also sovran), supreme;

Antonyms

last, least;

Near Antonyms

inconsequential, inconsiderable, insignificant, minor, negligible, slight, trifling, trivial, unimportant;

collateral, inferior, secondary, subordinate, subsidiary;

Related Words

distinguished, eminent, illustrious, noble, notable, noteworthy, outstanding, prestigious, signal, star, stellar, superior;

high-level, senior, top;

important, influential, major, mighty, momentous, significant;

incomparable, matchless, unequaled (or unequalled), unparalleled, unsurpassed;

celebrated, famed, famous, renowned;

3

key

verb

Definition of key

keyed; keying; keys
transitive verb
1 : to lock or secure with or as if with a key : fasten: such as
a : to secure (something, as a pulley on a shaft) by a key
b : to finish off (an arch) by inserting a keystone
2 : to regulate the musical pitch of
  • key the strings
3 : to bring into harmony or conformity : make appropriate : attune
  • remarks keyed to a situation
4 : to identify (a biological specimen) by a key (see 1key 3d)
5 : to provide with identifying or explanatory cross-references
  • instructions keyed to accompanying drawings
  • —John Gartner
6 : to make nervous, tense, or excited —usually used with up
  • was too keyed up to sleep
7 : to enter or input (text or data) by using a keyboard
  • keying changes to a manuscript
—often used with in or into
  • key in a password
  • information being keyed into a database
8 : to be essential to : play the most important part in
  • defense keyed the victory
9 : to vandalize by scratching with a key
  • someone keyed my car door
intransitive verb
1 : to use a key
2 : to observe the position or movement of an opposing player in football in order to anticipate the play —usually used with on
  • The middle linebacker was keying on the halfback.
3 : to operate a machine by means of a keyboard : keyboard

See key defined for English-language learners

Examples of key in a Sentence

  1. The changes to the manuscript are being keyed by the typist.

  2. her response was perfectly keyed to the situation

Origin and Etymology of key

see 1key

key Synonyms

Synonyms

accommodate, attune, conciliate, conform, coordinate, harmonize, reconcile;

Antonyms

disharmonize;

Near Antonyms

confuse, disarray, disorder, disorganize, disrupt, disturb, skew, upset;

alienate, estrange;

Related Words

adapt, tune;

blend, combine, connect, correlate, dovetail, fit, fuse, integrate, join, match, merge, orchestrate, pair, square, suit, synchronize, synthesize, unify, unite;

align (also aline), arrange, array, balance, equalize, even, order, proportion, regularize, standardize;

4

key

noun

Definition of key

: a low island or reef; specifically : any of the coral islets off the southern coast of Florida
  • the Florida Keys

Origin and Etymology of key

Spanish cayo, from Taino

Other Geology Terms

anthracite, boulder, cwm, erratic, igneous, intrusive, mesa, sedimentary, silt, swale

5

key

noun

Definition of key

slang
: a kilogram especially of marijuana or heroin

Origin and Etymology of key

by shortening & alteration from kilo

Other Drug/Tobacco Terms

controlled, flake, herb, sodden

Key

biographical name \ ˈkē \

Definition of Key

Francis Scott 1779–1843 American lawyer and author of "The Star-Spangled Banner"

Key

biographical name

Definition of Key

John (Phillip) 1961–     prime minister of New Zealand (2008–16)

Phrases Related to KEY

Related Phrases

KEY Defined for English Language Learners

key

verb

Definition of key for English Language Learners

  • : to enter (information) by using the keys of a computer, typewriter, etc.

  • : to have the most important part in (something)

key

adjective

Definition of key for English Language Learners

  • : extremely important

KEY Defined for Kids

1

key

noun \ ˈkē \

Definition of key for Students

1 : an instrument by which the bolt of a lock (as on a door) is turned or by which an engine is started
2 : a device having the form or function of a key
  • Can you wind the clock with the key?
3 : the thing that is necessary or most important in doing something
  • To learn a skill, practice is the key.
4 : something (as a map legend) that gives an explanation : solution
5 : one of the levers with a flat surface that is pressed with a finger to activate a mechanism of a machine or instrument
  • computer keys
6 : a system of seven musical tones arranged in relation to a keynote from which the system is named the key of C
2

key

verb

Definition of key for Students

keyed; keying
1 : to regulate the musical pitch of
2 : to bring into harmony
3 : to record or enter by operating the keys of a machine The cashier keyed in the price.
3

key

adjective

Definition of key for Students

: of great importance : most important
  • She is one of our key players.
4

key

noun

Definition of key for Students

: a low island or reef
  • the Florida Keys

Law Dictionary

key

adjective

legal Definition of key

: of vital importance (as in a business organization) especially so as to be specially insured to the benefit of an employer
  • key man
  • key employee insurance

Learn More about key

  1. See words that rhyme with key Thesaurus: All synonyms and antonyms for key Spanish Central: Translation of key Nglish: Translation of key for Spanish speakers Britannica English: Translation of key for Arabic speakers Britannica.com: Encyclopedia article about key

Seen and Heard

What made you want to look up key? Please tell us where you read or heard it (including the quote, if possible).

show hide

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

WORD OF THE DAY

cerulean

play

resembling the blue of the sky

Get Word of the Day daily email!

TRENDING NOW

  1. mistrial 'a trial that terminates without a verdict'

  2. hogwash 'nonsense, balderdash'

  3. probity 'adherence to the highest principles and ideals'

  4. sequacious 'intellectually servile'

  5. inadmissible 'not capable of being allowed'

SEE ALL

BROWSE DICTIONARY

kex
key
Key

Test Your Vocabulary

Difficult Spelling Words Quiz

  • alphabet-pasta-spelling-help
  • Which is the correct spelling?
Spell It

Can you spell these 10 commonly misspelled words?

TAKE THE QUIZ
Word Winder's CrossWinder

Test Your Knowledge - and learn some interesting things along the way.

TAKE THE QUIZ

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

Words at Play

Ask the Editors

Word Games