Capacity, n.; pl. Capacities
Etymology: [L. capacitus, fr. capax, capacis; fr. F. capacité. See Capacious.]
1. The power of receiving or containing; extent of room or space; passive power; -- used in reference to physical things. Had our great palace the capacity To camp this host, we all would sup together. Shak. The capacity of the exhausted cylinder. Boyle.
2. The power of receiving and holding ideas, knowledge, etc.; the comprehensiveness of the mind; the receptive faculty; capability of undestanding or feeling. Capacity is now properly limited to these [the mere passive operations of the mind]; its primary signification, which is literally room for, as well as its employment, favars this; although it can not be dented that there are examples of its usage in an active sense. Sir W. Hamilton.
3. Ability; power pertaining to, or resulting from, the possession of strength, wealth, or talent; possibility of being or of doing. The capacity of blessing the people. Alex. Hamilton. A cause with such capacities endued. Blackmore.
4. Outward condition or circumstances; occupation; profession; character; position; as, to work in the capacity of a mason or a carpenter.
3 more senses
5. (Law)
Legal or noral qualification, as of age, residence, character, etc., necessary for certain purposes, as for holding office, for marrying, for making contracts, will, etc.; legal power or right; competency. Capacity for heat, the power of absorbing heat. Substances differ in the amount of heat requisite to raise them a given number of thermometric degrees, and this difference is the measure of, or depends upon, whzt is called their capacity for heat. See Specific heat, under Heat.
Syn. -- Ability; faculty; talent; capability; skill; efficiency; cleverness. See Ability.
Shades of meaning
Fernald has no entry of its own for capacity; he lists it under power.
Where he writes about it:
Power and ability include capacity, which is power to receive; but ability is often distinguished from capacity, as power that may be manifested in doing, as capacity is in receiving; one may have great capacity for acquiring knowledge, and yet not possess ability to teach. — from power
Our abilities include our natural capacity, faculties, and talents, with all the dexterity, skill, and readiness that can be acquired. — from power