key Definition

  • 1a small piece of shaped metal with incisions cut to fit the wards of a particular lock, which is inserted into a lock and turned to open or close it.
  • 2a button on a typewriter or computer keyboard that is pressed to input a character or perform a specific function.
  • 3a set of musical notes or tones arranged in a particular pattern and used as the basis for a composition, typically consisting of a scale, a mode, and a set of rhythms.

Using key: Examples

Take a moment to familiarize yourself with how "key" can be used in various situations through the following examples!

  • Example

    I can't find the key to my front door.

  • Example

    The key to success is hard work and dedication.

  • Example

    Press the 'Enter' key to submit your answer.

  • Example

    The song is written in the key of C major.

key Synonyms and Antonyms

Synonyms for key

Antonyms for key

Idioms Using key

  • to have the power or ability to unlock or solve a problem or mystery


    The missing piece of evidence could hold the key to solving the case.

  • in tune or in harmony with the rest of a musical performance


    The choir sang beautifully and were always on key.

  • to start a vehicle or machine by turning a key in the ignition


    He turned the key and the engine roared to life.

Phrases with key

  • to enter data or information into a computer or other electronic device by pressing keys


    She keyed in the password and logged into her account.

  • an honor bestowed upon esteemed visitors or residents of a city, granting them the freedom of the city


    The mayor presented the actor with the key to the city during his visit.

  • a set of sharp or flat symbols placed on the staff at the beginning of a piece of music, indicating the key in which the music is written


    The key signature of this piece is B-flat major.

Origins of key

from Old English 'cǣg', meaning 'key, metal instrument for locking or unlocking'


Summary: key in Brief

The term 'key' [kiː] refers to a small metal instrument used to lock or unlock something, or a button on a keyboard used to input characters. It can also refer to a set of musical notes used as the basis for a composition. Phrases like 'key in' and 'key to the city' extend its meaning, while idioms like 'hold the key to something' and 'on key' denote power and harmony, respectively.

How do native speakers use this expression?