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capacity

/kəˈpæsəti//kəˈpasɪti/·noun
the maximum amount that something can hold, produce, or do
Fig. 1 — I watch the same strong figure holding a loaded bar locked high overhead, and one by one another plate slides onto each end — and with every plate a tall gauge beside the lifter climbs another notch and the arms tremble a little harder.
01Definition

Capacity is the most a thing can take — from the Latin capax, 'able to hold'. It names an outer limit: the capacity of a stadium, a factory's production capacity, a person's capacity for work. Where ability looks at the skill to perform, capacity measures the ceiling — how much, at the very most. Push past a container's capacity and it overflows; a network already at full capacity cannot expand to carry one more call until a wider threshold is built.

02In use
  • iThe concert hall has a seating capacity of two thousand.
  • iiYears of training increased her capacity to cope with stress.
  • iiiBy late August the reservoir had filled almost to capacity.
03Collocations
  • full capacity
  • seating capacity
  • production capacity
  • capacity for
  • at capacity

Family capacious (adjective) · capacitor (noun)

04Relations

=capability, volume, potential, room, ability

≠incapacity

05Compared
PairThe difference
capacity vs abilityability is the skill in action (what you can do); capacity is the upper limit (how much, at most).
06TOEFL & IELTS

A high-value academic noun, usually about limits and quantities: 'production capacity', 'at full capacity', 'capacity for change'. The exam trap is ability: ability is the skill to do something, while capacity is the maximum amount or the potential — 'the ability to learn' versus 'a large capacity for learning'. It is also common in science (heat capacity, lung capacity). The adjective capacious means roomy.

07Asked
What does 'in my capacity as' mean?
Acting in a particular official role: in her capacity as chair, she signed the order — the signature belongs to the role, not the private person. The phrase is fixed with as (not 'of'), and it exists to separate hats: the same person can refuse as a friend what they must approve in their capacity as manager.
What is the difference between capacity and capability?
Capacity asks how much; capability asks what kinds. A factory's capacity is the volume it can turn out at its limit; its capabilities are the range of things it knows how to make. Business writing keeps the pair apart deliberately — you expand capacity by adding resources, but you build capability by adding skills.
What does running 'at full capacity' mean?
Operating at the very ceiling — every seat, bed or machine in use, nothing spare. The scene above puts a number on the idea: plate by plate the lifter's gauge climbs, until one more plate would not raise the reading — it would end the lift. Past that point a system does not do more; it overflows, queues or fails, which is why 'at full capacity' is a warning as often as a boast.
Is capacity the same as ability?
No — ability is the skill to do a thing, capacity is the ceiling on how much of it you can do, and the two are pulled apart properly on the ability vs capacity page in the 'Compared' list above.
Is it 'in my capacity as' or 'in my capacities as'?
Singular, almost always — one role per act: in my capacity as editor. The plural appears only when someone genuinely acts in several roles at once ('in her capacities as founder and trustee'), and even then many writers prefer repeating the singular. Each role is its own capacity; count the hats and the grammar follows.
What does capacity mean in law?
The recognized competence to perform a legal act — to sign a contract, make a will, stand trial. A child generally lacks full capacity to contract; a patient's mental capacity can be assessed before consent counts. It is the same ceiling metaphor turned formal: not what you are able to do, but what the law will let your signature carry.