Lesson
A lesson in school is a planned period of time for learning. It involves one or more students being taught by a teacher. A lesson may be either one section of a textbook or a period of time during which learners are taught about a subject or how to perform an activity. Lessons are mostly taught in a classroom but they may take place online, or outside. Not all lessons are for children.
A lesson means someone learning something he did not know before. Such a lesson can be either planned or accidental, enjoyable or painful. The slang phrase "to teach someone a lesson", means to punish or scold a person for a mistake they have made making sure that he does not make the same mistake again.
Lessons can also be made entertaining. When the term education is combined with entertainment, it is called "edutainment".