suggestion vs proposal

suggestion and proposal both are nouns.

Word	Noun	Adjective	Verb	Adverb
suggestion	Yes	No	No	No
proposal	Yes	No	No	No

As nouns, proposal is a hypernym of suggestion; that is, proposal is a word with a broader meaning than suggestion:

suggestion (noun)	proposal (noun)
the act of inducing hypnosis	something proposed (such as a plan or assumption)
an idea that is suggested	the act of making a proposal
the sequential mental process in which one thought leads to another by association	an offer of marriage
a proposal offered for acceptance or rejection
persuasion formulated as a suggestion
a just detectable amount