lunatic vs loony

lunatic and loony both are nouns.

Word	Noun	Adjective	Verb	Adverb
lunatic	Yes	Yes	No	No
loony	Yes	Yes	No	No

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

Other hyponyms of lunatic include crazy, looney, nutcase, weirdo, bedlamite, pyromaniac, madwoman, madman.

lunatic (noun)	loony (noun)
an insane person	someone deranged and possibly dangerous
a reckless impetuous irresponsible person

lunatic (adjective)	loony (adjective)
insane and believed to be affected by the phases of the moon	informal or slang terms for mentally irregular