ex ‧ ten ‧ sion S3 W3 /ɪkˈstenʃ ə n/ BrE AmE noun
1 . MAKING SOMETHING BIGGER OR LONGER [uncountable and countable] the process of making a road, building etc bigger or longer, or the part that is added
the extension of the Jubilee underground line
2 . EXTRA ROOMS [countable] British English another room or rooms which are added to a building
the planned extension to the National Museum
a loft extension
3 . EXTRA TIME [countable usually singular] an additional period of time allowed for something:
Donald’s been given an extension to finish his thesis.
The pub’s got an extension tonight (=it will stay open longer than usual) .
4 . INCLUDE/AFFECT MORE THAN BEFORE [singular, uncountable] the development of something in order to make it affect more people, situations, areas than before
the extension of the copyright laws to cover online materials
an extension of the powers of the European Parliament
5 . TELEPHONE [countable]
a) one of many telephone lines connected to a central system in a large building, which all have different numbers:
Can I have extension 316, please?
Do you know Mr Brown’s extension number?
b) one of the telephones in a house that all have the same number
6 . by extension used when you want to mention something that is naturally related to something else:
My primary responsibility is to the pupils, and by extension to the teachers and parents.
7 . extensions [plural] long pieces of artificial hair that can be attached to your hair to make it look longer
8 . COMPUTER [countable] technical a set of three letters that follow the name of a computer ↑ file to show what it is. For example, the extension ‘.doc’ shows that a file is a written document.
9 . ELECTRIC WIRE [countable] British English an ↑ extension lead
10 . STRETCH ARM/LEG [uncountable and countable] the position of a part of the body when it is stretched, or the process of stretching it
11 . UNIVERSITY/COLLEGE [uncountable] part of a university or college that offers courses to people who are not full-time students