pyjama vs sleepwear

pyjama and sleepwear both are nouns.

Word	Noun	Adjective	Verb	Adverb
pyjama	Yes	No	No	No
sleepwear	Yes	No	No	No

As nouns, sleepwear is a hypernym of pyjama; that is, sleepwear is a word with a broader meaning than pyjama:

pyjama: (usually plural) loose-fitting nightclothes worn for sleeping or lounging; have a jacket top and trousers
sleepwear: garments designed to be worn in bed

Other hypernyms of pyjama include nightclothes, nightwear.

pyjama (noun)	sleepwear (noun)
(usually plural) loose-fitting nightclothes worn for sleeping or lounging; have a jacket top and trousers	garments designed to be worn in bed
a pair of loose trousers tied by a drawstring around the waist; worn by men and women in some Asian countries