extension · noun C /ɪkˈsten.tʃən/Full view
extension (EXTRA TIME)
B2 extra time that you are given to do or use something
Dictionary example:

I've applied for an extension of my visa.

extension (TELEPHONE)
B2 a telephone that is connected to the main telephone in an office or other large building
Dictionary example:

Call me on extension 3104.

Learner example:

For further information call 990-643 extension 93. (First Certificate in English; B2; Greek)

extension (DEVELOPMENT)
B2 something that has developed as a result of something else
Dictionary example:

The book is an extension of ideas he set out in an earlier article.

Learner example:

So we might say the computer is the extension of our brain. (First Certificate in English; B2; Chinese)

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