noun

• (uncountable) The state or quality of being active; activeness.
  "Pit row was abuzz with activity."
• (countable) Something done as an action or a movement.
  "The activity for the morning was a walk to the store."
• (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."
• (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."