maniac vs looney

maniac and looney both are nouns.

Word	Noun	Adjective	Verb	Adverb
maniac	Yes	Yes	No	No
looney	Yes	No	No	No

As nouns, looney is a hyponym of maniac; that is, looney is a word with a more specific, narrower meaning than maniac:

Other hyponyms of maniac include crazy, loony, nutcase, weirdo, bedlamite, pyromaniac, madwoman, madman.

maniac (noun)	looney (noun)
an insane person	someone deranged and possibly dangerous
a person who has an obsession with or excessive enthusiasm for something

maniac (adjective)	looney (adjective)
wildly disordered