promise vs speech act

promise and speech act both are nouns.

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

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

promise: a verbal commitment by one person to another agreeing to do (or not to do) something in the future
speech act: the use of language to perform some act

Other hypernyms of promise include commitment, dedication.

promise (noun)	speech act (noun)
grounds for feeling hopeful about the future	the use of language to perform some act
a verbal commitment by one person to another agreeing to do (or not to do) something in the future

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