noun

key

kee

noun

A shaped piece of metal used to open or lock a particular lock.

"She forgot her house key at the office again."

"He cut a spare key for his sister."

The single most important factor or step needed to achieve something.

"Practice is the key to learning any instrument."

"Patience was the key to solving the puzzle."

One of the buttons pressed to type on a keyboard or play a musical instrument.

"The space bar is the widest key on the keyboard."

"He pressed a wrong key and the whole document changed."

A short guide listing what the symbols, colours, or abbreviations on a map, chart, or test mean.

"Check the key at the bottom of the map to see what the blue lines mean."

"The teacher provided an answer key for the exam."

In music, the set of related notes a piece is built around, giving it its overall tonal centre.

"The song shifts from a major key to a minor one in the bridge."

"She transposed the piece into a lower key."

A code or piece of information used to lock or unlock encrypted data.

"The website uses a private key to secure your login details."

adj

Central or essential; of major importance.

"Cost was a key factor in choosing the smaller car."

"She played a key role in launching the new product."

How to Use Key

Learner’s notes

In plain EnglishMost often either the metal object that opens a lock, or (as an adjective) something essential and central to a situation.

Common mistake

Don't confuse the geographic sense (a low island, as in "the Florida Keys") with the everyday lock-opening object — they're unrelated in origin.

Common pairings

key to success a key role turn the key key factor

Word Forms

keyer comparative, more key comparative, keys plural, keys plural, keys plural, keyest superlative, most key superlative

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She forgot her house _____ at the office again.

Etymology

From Old English cæg, of uncertain deeper origin, though it may ultimately trace back to a root meaning "stake" or "peg" — early keys were simple rods used to lift a bar across a door.

Rhymes for key

ey hey bey dey ley fey ney Rey grey they joey whey

See all rhymes for key →