proposal vs proposal of marriage

proposal and proposal of marriage both are nouns.

Word	Noun	Adjective	Verb	Adverb
proposal	Yes	No	No	No
proposal of marriage	Yes	No	No	No

As nouns, proposal and proposal of marriage are synonyms defined as:

Other synonyms of proposal include marriage offer, marriage proposal.

proposal (noun)	proposal of marriage (noun)
something proposed (such as a plan or assumption)	an offer of marriage
the act of making a proposal
an offer of marriage