To impart knowledge or skill to someone by instruction or example.
She teaches mathematics at the local high school.
To cause someone to learn or understand something by example or experience.
The difficult situation taught him the value of patience.
To advocate or preach a particular doctrine or belief.
The monk teaches the principles of Buddhism to his followers.
To punish, reprimand, or otherwise discipline someone so that they will not repeat an unwanted behaviour (often followed by an infinitive beginning with "to").
"That ought to teach you not to leave your bike unlocked again."