The word set has many meanings:

1. To put something in a particular place or position. You might set a book on the table, set a vase of flowers by the window, or set your alarm clock for 6:30 AM. When the sun sets, it moves down below the horizon at the end of the day.
2. To establish or decide something. A teacher sets the rules for classroom behavior. A coach sets the lineup for the game. Your parents might set a time when you need to be home. When you set a goal, you decide what you want to achieve and commit to working toward it.
3. To prepare or arrange something for use. A stage crew sets the stage before a play begins, arranging furniture and props. You set the table before dinner by putting out plates, silverware, and glasses. A jeweler sets a diamond in a ring by securing it in place.
4. To harden or become firm. Concrete sets as it dries, becoming solid and strong. Jello sets in the refrigerator. When a broken bone sets, it heals in the correct position.
5. A collection of things that belong together. A set of dishes includes plates, bowls, and cups that match. A set of encyclopedias contains all the volumes in the series. In mathematics, a set is a group of numbers or objects, like the set of even numbers or the set of primary colors.
6. A group of games in tennis. Players compete in sets, and whoever wins the most sets wins the match.