To forbid means to order someone not to do something, or to make something against the rules. When your parents forbid you from watching a certain TV show, they're telling you it's not allowed. When a teacher forbids talking during a test, she's making it clear that silence is required.

The word carries weight and authority. A principal might forbid running in the hallways. A law might forbid certain actions. During World War II, rationing rules forbade buying more than a limited amount of sugar or gasoline. The opposite of forbid is permit or allow.

Forbidden describes something that has been ruled off-limits. A forbidden area in a museum means you absolutely cannot enter it. Kids often find forbidden things more tempting, like the forbidden cookie jar or a forbidden room in a house.

The past tense is a bit unusual: forbade. “My coach forbade us from practicing until we finished our homework.” People also use forbidden as a past participle: “She had forbidden him from borrowing her bike.”

When something is strictly and seriously not allowed, especially by an important authority, that's when you use forbid rather than lighter words like “don't” or “please avoid.”