key

1 of 5

noun (1)

ˈkē 

plural keys

1

a

: a usually metal instrument that is used to open a lock or to start or access a mechanism

my house/car keys

turned the key in the lock/ignition

… a metallic rattle, like keys being jangled.

—Derwent May

b

: something that resembles a key in form or function

a key for winding a clock

A computer chip-based ignition key that relies on a wireless connection to your car …

—Dustin Hawley

By using their smartphone, … guests are able to … download a room key.

—Sharon Love

see also key card, key fob

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

ˈkēd 

adjective

keyless

ˈkē-ləs 

adjective

key

2 of 5

adjective

: extremely or crucially important

key issues

a key moment in the game

a key member of the staff

key

3 of 5

verb

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 key entry 1 sense 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

key

4 of 5

noun (2)

: a low island or reef

specifically : any of the coral islets off the southern coast of Florida

the Florida Keys

key

5 of 5

noun (3)

slang

: a kilogram especially of marijuana or heroin

Synonyms

Noun (1)

• legend

Adjective

• arch
• big
• capital
• cardinal
• central
• chief
• dominant
• first
• foremost
• grand
• great
• greatest
• highest
• leading
• main
• master
• number one
• No. 1
• numero uno
• overbearing
• overmastering
• overriding
• paramount
• predominant
• preeminent
• premier
• primal
• primary
• principal
• prior
• sovereign
• sovran
• supreme

Verb

• accommodate
• attune
• conciliate
• conform
• coordinate
• harmonize
• reconcile

Examples of key in a Sentence

Noun (1)

in order to know what those dotted lines represent, you'll need to look at the key

a good education is the key to success

he had found the key to her heart

Adjective

He's a key player in the organization.

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

Underline key words and phrases as you read.

Their votes were key in getting the bill passed.

Verb

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

her response was perfectly keyed to the situation

Recent Examples on the Web

Adjective

But competition is fierce, and differentiation will be key. —Ethan Stone, USA Today, 19 Apr. 2025

However, slowing the progression of vision loss is key. —Heidi Cope, Health, 19 Apr. 2025

Verb

At the time of the incident, police released video showing a man keying a Tesla, along with still images of him walking through the lot in a blue shirt and sitting in a dark-colored Chevrolet, the Bradenton Herald previously reported. —Michael Moore Jr., Miami Herald, 20 Apr. 2025

Sentry Mode video showed a man keying the vehicle while walking past. —Peter D'abrosca, FOXNews.com, 12 Apr. 2025

Noun

The key is to ensure smartphone users know never to take or make these calls. —Zak Doffman, Forbes.com, 20 Apr. 2025

The urge to indulge our five senses is strong, but the key is to slow down and savor the moment, whether that’s lounging under the sun or finding peace in the stillness. —Valerie Mesa, People.com, 19 Apr. 2025

Word History

Etymology

Noun (1), Adjective, and Verb

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

Noun (2)

Spanish cayo, from Taino

Noun (3)

by shortening & alteration from kilo

First Known Use

Noun (1)

before the 12th century, in the meaning defined at sense 1a

Adjective

1832, in the meaning defined above

Verb

14th century, in the meaning defined at transitive sense 1

Noun (2)

1693, in the meaning defined above

Noun (3)

1966, in the meaning defined above

Phrases Containing key

• Allen key
• Alt key
• chroma-key
• church key
• control key
• delete key
• dichotomous key
• escape key
• function key
• hold the master key
• hot key
• key card
• key chain
• key club
• key deer
• key fob
• key grip
• key light
• key lime
• key lime pie
• key ring
• key signature
• key to
• key word
• low-key
• master key
• off-key
• pound key
• public-key
• shift key
• skeleton key
• tab key
• under lock and key

Rhymes for key

• be
• bee
• bree
• cree
• fee
• flea
• flee
• free
• gee
• ghee
• glee
• he

Kids Definition

key

1 of 4 noun

ˈkē 

plural keys

1

a

: a small device that is used to open a lock or start an automobile

b

: a device having the form or function of a key

a key for winding a clock

2

: a means of gaining or preventing entrance, possession, or control

3

a

: something that provides an explanation, solution, or means of identifying

the key to a riddle

b

: a series of phrases or statements that describe characteristics by which plants or animals of a particular group differ and are used to aid in identification

c

: a map legend

4

: one of the levers with a flat surface that is pressed by a finger in operating a machine or playing an instrument

5

: a system of seven musical tones arranged in relation to a keynote from which the system is named

the key of C

6

: a characteristic style or tone

7

: a small switch for opening or closing an electric circuit

key

2 of 4 verb

keyed; keying

1

: to adjust the musical pitch of

2

: to bring into harmony

3

: to make nervous, tense, or excited

—usually used with up

all keyed up about the test

4

: to record by operating the keys of a machine

key each price into the cash register

key

3 of 4 adjective

: of great importance

the key people in the organization

the key question is "Can we afford it?"

use key words in an outline

key

4 of 4 noun

: a low island or reef

the Florida Keys

Etymology

Noun

Old English cǣg "key"

Noun

from Spanish cayo "a low island or reef"

Legal Definition

key

adjective

: 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

Biographical Definition

Key 1 of 2

biographical name (1)

ˈkē 

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

Key

2 of 2

biographical name (2)

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