Cambridge Dictionaries online Cambridge Dictionaries online

The most popular online dictionary and thesaurus for learners of English

English definition of “key”

key

noun  /ki/ us  

key noun (METAL SHAPE)

[C] a piece of metal cut into a special shape to fit into a lock where it can be turned to open something, such as a door, or to start something, such as a car engine: I put the key into the ignition.

key noun (MOVABLE PART)

[C] any of the set of movable parts that you press with your fingers on a computer or other machine to produce letters, numbers, or symbols, or on a musical instrument to produce sound: piano keys Press the shift key to write in capital letters.

key noun (IMPORTANT PART)

[U] the most important part of achieving something or explaining a situation: Revision is the key to good writing.

key noun (MUSICAL NOTES)

music [C] a set of musical notes based on one particular note: the key of C

key noun (LIST OF SYMBOLS)

[C] a list of the symbols used in a map or book with explanations of what they mean: The key is printed at the bottom of the page.
key
adjective  /ki/ us  
Deception is a key element of military strategy.
(Definition of key from the Cambridge Academic Content Dictionary © Cambridge University Press)
What is the pronunciation of key?
Add Cambridge dictionaries to your browser to your website

Definitions of “key” in other dictionaries

Word of the Day

improvisation

a performance that an actor, musician, etc. has not practised or planned

Word of the Day

Blog

Read our blog about how the English language behaves.

Learn More

New Words

Find words and meanings that have just started to be used in English, and let us know what you think of them.

Learn More