Refers to the maximum number of people or things a space, facility, or container can hold. Common in contexts like venues, shelters, prisons, or storage.
The capacity of this venue is 500 people.
The shelter's capacity has been exceeded.
定員 is the specific numeric capacity set for a vehicle or venue, whereas 収容能力 is the more general concept of how much a place can accommodate.
Compound of 収容 (しゅうよう, 'accommodation, housing') and 能力 (のうりょく, 'ability, capacity'). The word is a straightforward Sino-Japanese compound.