1. To add a new room or building to an existing building. English = extend.
2. To make something longer or bigger, especially by moving a boundary marking, fence or wall. English = extend.
3. To allow more time in which some activity is to be completed; to give an extension; to give additional time.
4. To be something which is added on to a space, building or period of time. English = (be) additional, (be) extra.