1. Amount of room or space inside; largest amount that can be held by a container: A gallon can has a capacity of four quarts.
2. The ability to receive, hold, or absorb the maximum amount that can be contained or produced: The capacity of the theater was 1500 seats and it was usually filled to capacity.
3. The capability to learn or to do; power or fitness: Sabina has a great capacity for learning.
4. The ability to withstand some force or to perform some function: Metal is known for its capacity to retain heat.
5. Maximum output: During the war, steel factories worked at full capacity.
6. A position or relation; legal power or qualification: A person may act in the capacity of a guardian, trustee, voter, friend, etc.
7. Etymology: from Latin capacitatem, capacitas, "breadth, spacious"; from capax, "able to hold much"; from capere "to take".

The maximum power, usually 3-5 times the rated power: A surge capacity can be provided to an electrical system over a short time without damage to the system.