extra

Something that is more than what you expected; exceeding; additional.

Example: I always put extra ketchup on my hamburger.

If something is extra good, large, special, etc., it is more so than normal.

Example: This shirt is extra large; it's too big for me.

An extra is a feature that you usually pay more for when you buy something.

Example: She got the car with all the sporty extras.

An extra is a person appearing in a movie who is not listed in the credits.