supposed vs alleged

supposed and alleged both are adjectives.

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

As adjectives, supposed and alleged are synonyms defined as:

Other synonyms of supposed include so-called.

supposed (adjective)	alleged (adjective)
required or under orders	declared but not proved
doubtful or suspect	doubtful or suspect
based primarily on surmise rather than adequate evidence
mistakenly believed