illegal

The word “illegal” means against the law; not authorised or permitted by legislation. In plain terms, not permitted by the law — the opposite of legal.

“Illegal” is pronounced ih-LEE-guhl (/ɪˈli.ɡəl/ in IPA).

Here is “illegal” used in a sentence: “It is illegal to drive without a valid licence.”

Words with a similar meaning to “illegal” include illegal immigrant.

“Illegal” is an adjective.

The word “illegal” comes from Medieval Latin. Borrowed from French illégal, from Medieval Latin illegalis — "not" (il-) + "legal" (legalis).

“Illegal” is a fairly common word in modern English, usually learned at around the A2 level.

Illegal means specifically against the law — forbidden by legislation, like driving without a license. Illicit is broader: it covers anything forbidden by law, custom, or morality, and often carries a sense of secrecy or disapproval, as in an illicit affair. Everything illegal is illicit, but not everything illicit is strictly illegal.

The two overlap heavily and are often interchangeable, but there is a shade of difference. Illegal usually means expressly forbidden by a specific statute or criminal law. Unlawful is a touch broader, covering anything not permitted by law, including acts that break civil rules without being outright crimes. In everyday speech, most people treat them as synonyms.

The direct opposite is legal — allowed and recognized by law. Related words include "lawful," "permitted," and "authorized." Something legal complies with the rules and carries no penalty, whereas something illegal breaks them and can be punished. The pair marks the basic line between what the law allows and what it forbids.