pj's vs pyjama

pj's and pyjama both are nouns.

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

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

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

Other synonyms of pj's include jammies, pajama.

pj's (noun)	pyjama (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