marriage offer vs proposal of marriage

marriage offer and proposal of marriage both are nouns.

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

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

Other synonyms of marriage offer include marriage proposal, proposal.

marriage offer (noun)	proposal of marriage (noun)
an offer of marriage	an offer of marriage