Extension (noun)

1. The action or process of extending something.
2. An additional part or feature added to something to enlarge or prolong its use.

Origin:

Late middle english: from latin extensio(n-), from the verb extendere (see extend).

Examples:

1. The extension of the deadline was granted.
2. The company's new product is an extension of the existing line.
3. The extension of the building added more office space.
4. The phone company offered him an extension on his contract.
5. The government announced an extension of the program to help small businesses.