Required means necessary or mandatory: something you must do, not something you can choose to skip. When homework is required, you have to complete it. When a book is required reading for English class, everyone needs to read it before the discussion.

The word comes from situations where someone with authority sets clear expectations. Your school might require students to wear uniforms. A soccer league might require players to attend practice twice a week. A recipe might require three eggs and two cups of flour.

Notice the difference between required and merely suggested or recommended. Your teacher might recommend bringing colored pencils to art class, but if pencils are required, you'll need them to complete the assignment. A museum might have a suggested donation, but if admission is required, you can't enter without paying.

Sometimes we use required to describe what's naturally necessary rather than officially mandatory. You might say courage is required to stand up to a bully, or patience is required to learn piano. In these cases, you mean these qualities are essential for success, even though no authority figure is enforcing the requirement.

The word can also appear as a noun: something that is a requirement. Completing all assignments might be a requirement for passing fifth grade.