promise vs betrothal

promise and betrothal both are nouns.

Word	Noun	Adjective	Verb	Adverb
promise	Yes	No	Yes	No
betrothal	Yes	No	No	No

As nouns, betrothal is a hyponym of promise; that is, betrothal is a word with a more specific, narrower meaning than promise:

promise: a verbal commitment by one person to another agreeing to do (or not to do) something in the future
betrothal: a mutual promise to marry

Other hyponyms of promise include oath, parole, word, word of honor, engagement, troth, pinning, rain check.

promise (noun)	betrothal (noun)
grounds for feeling hopeful about the future	the act of becoming betrothed or engaged
a verbal commitment by one person to another agreeing to do (or not to do) something in the future	a mutual promise to marry

promise (verb)	betrothal (verb)
make a promise or commitment
promise to undertake or give
make a prediction about; tell in advance
give grounds for expectations