Meaning of “promise” - Learner’s Dictionary

promise

verb us uk /ˈprɒmɪs/
The children can only come if they promise to behave themselves.The government has promised a thorough investigation of the matter.They promised to keep her identity secret.Both sides in the conflict have promised to try to avoid civilian casualties.I'm sorry I missed your birthday. I promise I'll make it up to you.
SAY [ I, T ]

B1 to say that you will certainly do something or that something will certainly happen:

[ + to do sth ] She promised to write to me every week.
[ + (that) ] Paul promised me that he'd cook dinner tonight.
GIVE [ + two objects ]

B1 to say that you will certainly give something to someone:

They promised us a reward.
Grandma's ring was promised to me.
promise to be sth

B2 If something promises to be good, exciting, etc, people expect that it will be good, exciting, etc.:

It promises to be a really exciting game.

(Definition of “promise verb” from the Cambridge Learner’s Dictionary © Cambridge University Press)