What does "key" mean?

1. (for a lock) a small piece of metal used to open a lock or start a car. 2. (on a keyboard) one of the buttons you press on a computer, phone, or piano. 3. (a solution or secret) the most important thing that helps you understand or achieve something. 4. (a guide or legend) a list of symbols or answers that explains what things mean on a map or in a book. 5. (music scale) a set of musical notes that a piece of music is based on. 6. (small island) a small, low island, especially in the Caribbean or near Florida. 7. (very important) the most important or necessary part of something. 8. (to type in) to type information into a computer or device. 9. (to scratch a car) to damage a car by scratching the paint with a key.

key — meaning, definition & examples

Q: Is it correct to say "the key of the problem"?

No — say "the key to the problem". In its abstract sense meaning 'a crucial element', 'key' takes the preposition 'to', not 'of'.

Word

01for a lock

A1 · Beginner Countable noun

n. a small piece of metal used to open a lock or start a car.

n. a metal instrument specifically shaped to operate the bolt of a lock.

“He reached into his pocket and realized he had left his house keys at the office.”

“The landlord handed over a heavy ring of keys, explaining which ones accessed the main gate and which opened the basement storage.”

Synonyms

openerlatchkey

02on a keyboard

A2 · Elementary Countable noun Computing

n. one of the buttons you press on a computer, phone, or piano.

n. any of the buttons or levers on a keyboard, typewriter, or musical instrument that are depressed to produce a character or sound.

“If the screen freezes, try pressing the escape key to close the program.”

“The pianist's fingers flew across the ivory keys, executing the complex concerto with remarkable precision and emotional depth.”

Synonyms

button

03a solution or secret

B1 · Intermediate Countable noun

n. the most important thing that helps you understand or achieve something.

n. a crucial factor or explanation that provides a solution or means of understanding.

“Hard work and a bit of luck were the keys to her success in business.”

“Identifying the primary motive of the suspect proved to be the key to solving the long-running investigation.”

Synonyms

secret solution clue

04a guide or legend

B1 · Intermediate Countable noun

n. a list of symbols or answers that explains what things mean on a map or in a book.

n. an explanatory list of symbols used in a map, table, or chart; also a set of answers to a test.

“Check the key at the bottom of the map to see what the different colors represent.”

“The textbook includes an answer key in the back so students can check their progress on the practice exercises.”

Synonyms

legend guide index

05music scale

B2 · Upper Intermediate Countable noun Music

n. a set of musical notes that a piece of music is based on.

n. a group of notes based on a particular note and comprising a scale, serving as the harmonic foundation of a composition.

“The song is written in the key of C major, so it sounds quite happy.”

“The singer requested a transposition because the original key was slightly outside her comfortable vocal range.”

Synonyms

scaletonality

06small island

C1 · Advanced Countable noun American English

n. a small, low island, especially in the Caribbean or near Florida.

n. a low-lying island or reef, often composed of coral or sand.

“We spent our vacation exploring the different keys along the coast of Florida.”

“The archipelago consists of several uninhabited keys that serve as vital nesting grounds for local seabird populations.”

Synonyms

islet reef

07very important

B1 · Intermediate

adj. the most important or necessary part of something.

adj. of paramount importance; fundamental or essential to a system or result.

“Education is a key part of a child's development.”

“The CEO identified three key areas where the company needed to improve to remain competitive in the global market.”

Synonyms

essential crucial vital

Antonyms

minor unimportant

08to type in

B2 · Upper Intermediate Computing

v. to type information into a computer or device.

v. to enter data into a computer system using a keyboard.

“You need to key in your password before you can access the files.”

“The clerk spent the entire afternoon keying in the data from the paper applications into the new digital database.”

Synonyms

type input enter

09to scratch a car

B2 · Upper Intermediate Informal

v. to damage a car by scratching the paint with a key.

v. to vandalize the bodywork of a vehicle by scratching it with a metal key.

“He was angry and decided to key his ex-girlfriend's car.”

“The security footage showed a hooded figure walking past the parked vehicles and deliberately keying the side panels of the luxury sedan.”

Synonyms

scratchvandalize

Common phrases and expressions where native English speakers use the word “key” in context.

01. arise key 02. key determinant 03. key indicator 04. robust key

In its abstract sense, 'key' collocates with the preposition 'to' (e.g., 'the key to success').

the key of the problem

the key to the problem

In its abstract sense meaning 'a crucial element', 'key' takes the preposition 'to', not 'of'.

“The metal key has proved remarkably resilient, but as electronic locking devices become ever-more popular, are the days of the humble key numbered?”

BBC News 30 Oct 2014

From Middle English keye, kaye, keiȝe, from Old English cǣġ (“key, solution, experiment”) (whence also Scots key and kay (“key”)), from Anglo-Frisian Proto-West Germanic kaiju, of uncertain origin. The only sure cognates are Saterland Frisian Koai (“key”), West Frisian kaai (“key”), and North Frisian kai, koie (“key”). Possibly from Proto-Germanic kēgaz, kēguz (“stake, post, pole”), from Proto-Indo-European ǵogʰ-, ǵegʰ-, ǵegʰn- (“branch, stake, bush”), which would make it cognate with Middle Low German kāk (“whipping post, pillory”), and perhaps to Middle Dutch keige (“javelin, spear”) and Middle Low German keie, keige (“spear”). For the semantic development, note that medieval keys were simply long poles (ending in a hook) with which a crossbar obstructing a door from the inside could be removed from the outside, by lifting it through a hole in the door. Liberman has noted, however, "The original meaning of kaig-jo- was presumably 'pin with a twisted end.' Words with the root *kai- followed by a consonant meaning 'crooked, bent; twisted' are common only in the North Germanic languages."

From Spanish cayo, itself from Taíno cayo meaning "small island", by way of a variant spelling of cay.

From a clipping of kilogram, itself from Greek khīlioi "thousand" + French gramme, or directly from kilo- as a combining form. The abbreviation emerged in late 19th-century English, first attested 1870, as a convenient reduction for metric weights.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

NOUN

Key(A1)

decryption function key Island key down key in key in on key on key up padlock scale