This is the 19482nd most frequent Korean word.
약속하고
"약속하고" means "promising" or "making a promise."
Here, 약속하고 refers to 'having a commitment or plan' with a friend for dinner.
오늘 저녁에 친구와 약속하고 저녁식사를 할 것입니다.
Tonight, I will meet a friend as planned and have dinner.
In this case, 약속하고 means 'making a promise or verbal agreement' that he fails to fulfill.
그는 항상 약속하고 전혀 지키지 않아요.
He always makes promises but never keeps them.
Here, 약속하고 signifies 'making a mutual agreement or pledge' regarding actions or behaviors.