jammies vs pajama

jammies and pajama both are nouns.

Word	Noun	Adjective	Verb	Adverb
jammies	Yes	No	No	No
pajama	Yes	No	No	No

As nouns, jammies and pajama are synonyms defined as:

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

Other synonyms of jammies include pj's, pyjama.

jammies (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