Teach is a verb meaning to show, explain, instruct and generally impart knowledge to someone. Teaching can occur in a formal setting such as a lecture class, or in a casual exchange between a father and son, perhaps as they repair a car or fish off a pier.
Sometimes people teach others by the example of their behavior, without saying a word. Students can often teach each other very productively by working together in a classroom.
Many synonyms for teach exist that allow a writer or speaker to convey quite different impressions. Educate, instruct, train, and demonstrate are neutral terms that do not necessarily suggest specific emotions. Words like indoctrinate, inculcate, brainwash, and propagandize, however, produce negative images of forced learning or the use of teaching for questionable, maybe even harmful, purposes.
In China, the most famous teacher in all of Chinese history is Confucius, a man who lived about 2500 years ago. Because of Confucius, teachers in many Asian countries are highly admired and respected.
Teach comes from an Old English word that means “show, present, point out.” Teaching requires these same activities today, so it seems clear that the meaning of teach has not changed very much. The Spanish word for to teach is enseñar. Although teach and enseñar are not cognates, some synonyms for teach do have Spanish cognates.