extension Definition

1. The process of extending something, or the state of being extended.
2. An added part, that makes the original larger or longer.
3. A subsidiary or extra telephone, connected to the main line.
4. An extra period beyond an original time limit.
5. A scheme by which services, eg those of a university or library, are made available to non-members.

Example: an extension course
6. Range or extent.
7. logic.
The extent of the application of a term or the number of objects included under it. Opposite of intension.