1. To give one a solemn pledge or assurance that one will do something. You promised to cut the lawn today! Sorry, I can't come with you tonight. I promised to take my little sister to the movies.

2. To give one a solemn pledge or assurance that someone can have something. In this usage, a noun or pronoun is used between "promise" and "to" to specify what has been promised. Jenny promised her baseball card collection to me when she moves. I can't give this to you—I promised it to my nephew.