Open English Wordnet
Nouns
(n)action, activity, activenessthe state of being active“his sphere of activity”, “he is out of action”
(n)bodily process, body process, bodily function, activityan organic process that takes place in the body“respiratory activity”
(n)natural process, natural action, action, activitya process existing in or produced by nature (rather than by the intent of human beings)“the action of natural forces”, “volcanic activity”
(n)activeness, activitythe trait of being active; moving or acting rapidly and energetically“the level of activity declines with age”