altostratus cloud vs stratus

altostratus cloud and stratus both are nouns.

Word	Noun	Adjective	Verb	Adverb
altostratus cloud	Yes	No	No	No
stratus	Yes	No	No	No

As nouns, stratus is a hypernym of altostratus cloud; that is, stratus is a word with a broader meaning than altostratus cloud:

altostratus cloud: a stratus cloud at an intermediate altitude of 2 or 3 miles
stratus: a large dark low cloud

Other hypernyms of altostratus cloud include stratus cloud.

altostratus cloud (noun)	stratus (noun)
a stratus cloud at an intermediate altitude of 2 or 3 miles	a large dark low cloud