CAPACITY IS THE LIMIT OF A THING. We understand the notion through the ideas of containment, volume, and fullness (see Containment). When a container is holding or carrying as much as it can and nothing else can be put in, then it has reached its capacity. If we try to put more things into the same container, it would not be possible. This makes capacity a threshold or a point that, once exceeded, triggers a different effect or event from before. The notion starts with the amount of things in a contained volume. In an abstract sense, capacity has a relationship to performance in which capacity is the maximum quantity or range of activity that can be achieved by an entity. The limit or the threshold becomes more important, as exceeding capacity can have negative consequences. We use capacity as an important notion of measuring, evaluating, and understanding sustainability.