activity

Etymology

From Middle French activité, from Latin activitas. Equivalent to active + -ity.

noun

1. (uncountable) The state or quality of being active; activeness.
   Pit row was abuzz with activity.
2. (countable) Something done as an action or a movement.
   The activity for the morning was a walk to the store.
3. (countable) Something done for pleasure or entertainment, especially one involving movement or an excursion.
   An increasing number of sports activities are on offer at the university.
   Quilting can be an enjoyable activity.
   Like most human activities, ballooning has sponsored heroes and hucksters and a good deal in between. For every dedicated scientist patiently recording atmospheric pressure and wind speed while shivering at high altitudes, there is a carnival barker with a bevy of pretty girls willing to dangle from a basket or parachute down to earth. 2013-06-07, David Simpson, “Fantasy of navigation”, in The Guardian Weekly, volume 188, number 26, page 36
4. (grammar, semantics) The lexical aspect (aktionsart) of verbs or predicates that change over time and have no natural end point.
   […]distinctions among states of affairs are reflected to a striking degree in distinctions among Aktionsart types. That is, situations are expressed by state verbs or predicates, events by achievement verbs or predicates, and actions by activity verbs or predicates. 1997, Robert van Valin, Randy LaPolla, Syntax, page 92
5. (physics) The number of radioactive decays per unit time. Unit for it: becquerel or curie
6. The propery of substances to react with other substances