proposition vs speech act

proposition and speech act both are nouns.

Word	Noun	Adjective	Verb	Adverb
proposition	Yes	No	Yes	No
speech act	Yes	No	No	No

As nouns, speech act is a hypernym of proposition; that is, speech act is a word with a broader meaning than proposition:

proposition (noun)	speech act (noun)
a task to be dealt with	the use of language to perform some act
(logic) a statement that affirms or denies something and is either true or false
a proposal offered for acceptance or rejection
the act of making a proposal
an offer for a private bargain (especially a request for sexual favors)

proposition (verb)	speech act (verb)
suggest sex to