Addition (noun)

1. The action or process of adding something to something else.
2. Something added to something else.
3. The arithmetic operation of summing.
4. The process of including something as an extra or as part of a larger whole.
5. The state of being added to something else.

Origin:

Late middle english: from old french, or from latin additio(n-), from addere "add".

Examples:

1. The addition of salt will improve the flavor of the soup.
2. The new addition to the team is a valuable asset.
3. The building's addition is almost complete.
4. The addition of a new law will change the way things are done.
5. The addition of the new feature has made the app more popular.