(ăk-tĭv′ĭ-tē)
[Pronunciation]

1. The production of energy or motion; the state of being active.
The word activity describes various conditions: enzyme activity describes the rate of influence of an enzyme on a particular system; extravehicular activity indicates the actions of space travelers while outside a space vehicle; radiation activity indicates the energy produced by a source of radiation.
2. The use of time by an individual.

Subentries:
graded activity
leisure activity
meaning of activity
optical activity
pulseless electrical activity
purposeful activity