act vs act up

act is a noun but act up is not a noun.

Word	Noun	Adjective	Verb	Adverb
act	Yes	No	Yes	No
act up	No	No	Yes	No

act (noun)	act up (noun)
something that people do or cause to happen
a subdivision of a play or opera or ballet
a legal document codifying the result of deliberations of a committee or society or legislative body
a short performance that is part of a longer program
a manifestation of insincerity

act (verb)	act up (verb)
behave in a certain manner; show a certain behavior; conduct or comport oneself	make itself felt as a recurring pain
pretend to have certain qualities or state of mind	misbehave badly; act in a silly or improper way
discharge one's duties
play a role or part
perform on a stage or theater
behave unnaturally or affectedly
perform an action, or work out or perform (an action)
have an effect or outcome; often the one desired or expected
be suitable for theatrical performance