hypothetical vs suppositious

hypothetical is a noun but suppositious is not a noun.

Word	Noun	Adjective	Verb	Adverb
hypothetical	Yes	Yes	No	No
suppositious	No	Yes	No	No

As adjectives, hypothetical and suppositious are synonyms defined as:

hypothetical and suppositious: based primarily on surmise rather than adequate evidence

Other synonyms of hypothetical include conjectural, divinatory, hypothetic, supposed, suppositional, supposititious.

hypothetical (noun)	suppositious (noun)
a hypothetical possibility, circumstance, statement, proposal, situation, etc.

hypothetical (adjective)	suppositious (adjective)
based primarily on surmise rather than adequate evidence	based primarily on surmise rather than adequate evidence