basis vs supposition

basis and supposition both are nouns.

Word	Noun	Adjective	Verb	Adverb
basis	Yes	No	No	No
supposition	Yes	No	No	No

As nouns, supposition is a hypernym of basis; that is, supposition is a word with a broader meaning than basis:

basis: the fundamental assumptions from which something is begun or developed or calculated or explained
supposition: a hypothesis that is taken for granted

Other hypernyms of basis include assumption, supposal.

basis (noun)	supposition (noun)
the fundamental assumptions from which something is begun or developed or calculated or explained	a hypothesis that is taken for granted
a relation that provides the foundation for something	the cognitive process of supposing
the most important or necessary part of something	a message expressing an opinion based on incomplete evidence