extension
ex-ten-sion
noun
An additional part built onto an existing structure, often a house.
"They are building an extension on their house."
noun
A specific internal telephone line or number within a larger system.
"Please dial extension 205 for sales."
noun
The act of making something longer, larger, or later in time.
"We requested an extension to the project deadline."
Thesaurus
Synonyms: annex, annexe, wing, extension service, university extension, elongation, file name extension, filename extension, lengthiness, prolongation, extension phone, telephone extension