supposed vs suppositious

supposed and suppositious both are adjectives.

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

As adjectives, supposed and suppositious are synonyms defined as:

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

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

supposed (adjective)	suppositious (adjective)
required or under orders	based primarily on surmise rather than adequate evidence
doubtful or suspect
based primarily on surmise rather than adequate evidence
mistakenly believed