1.Definition: (chemistry) the capacity of a substance to take part in a chemical reaction

"Catalytic activity"

Category: General

2.Definition: a process existing in or produced by nature (rather than by the intent of human beings)

"The action of natural forces", "Volcanic activity"

Related Noun(s):action

Category: General

3.Definition: an organic process that takes place in the body

"Respiratory activity"

Category: General

4.Definition: any specific behavior

"They avoided all recreational activity"

Category: General

5.Definition: the state of being active

"His sphere of activity", "He is out of action"

Related Noun(s):action, activeness

Category: General

6.Definition: the trait of being active; moving or acting rapidly and energetically

"The level of activity declines with age"

Related Noun(s):activeness

Category: General