pj's vs pajama

pj's and pajama both are nouns.

Word	Noun	Adjective	Verb	Adverb
pj's	Yes	No	No	No
pajama	Yes	No	No	No

As nouns, pj's and pajama are synonyms defined as:

pj's and pajama: (usually plural) loose-fitting nightclothes worn for sleeping or lounging; have a jacket top and trousers

Other synonyms of pj's include jammies, pyjama.

pj's (noun)	pajama (noun)
(usually plural) loose-fitting nightclothes worn for sleeping or lounging; have a jacket top and trousers	(usually plural) loose-fitting nightclothes worn for sleeping or lounging; have a jacket top and trousers
	a pair of loose trousers tied by a drawstring around the waist; worn by men and women in some Asian countries