acting vs activity

acting and activity both are nouns.

Word	Noun	Adjective	Verb	Adverb
acting	Yes	Yes	No	No
activity	Yes	No	No	No

As nouns, activity is a hypernym of acting; that is, activity is a word with a broader meaning than acting:

Other hypernyms of acting include performing arts.

acting (noun)	activity (noun)
the performance of a part or role in a drama	any specific behavior
	the trait of being active; moving or acting rapidly and energetically
	an organic process that takes place in the body
	a process existing in or produced by nature (rather than by the intent of human beings)
	the state of being active
	(chemistry) the capacity of a substance to take part in a chemical reaction

acting (adjective)	activity (adjective)
serving temporarily especially as a substitute