B1adjectiveformal2K

Illegal

UK //ɪˈliːɡ(ə)l//US //ɪˈlɪɡəl//

Definition

Not allowed by law.

Examples

Driving without a license is considered illegal.
He faced severe penalties for his illegal activities.
Many countries have illegal drug trafficking problems.
It's illegal to park here without a permit.
The police cracked down on illegal gambling.
Entering the building after hours is illegal.
She reported the illegal emissions from the factory.
Illegal immigration laws are a controversial topic.
The government enforced strict laws against illegal fishing.
Illegal logging has devastated the rainforests.

Usage notes

Use 'illegal' in formal contexts, especially legal discussions, but also in general conversation. It's not appropriate for casual slang.

Grammar pattern

standalone adjective

Memory hint

Think of 'illegal' as 'against the law'—imagine a person breaking the law.

Collocations

illegal activity
illegal immigration
illegal drugs
illegal parking

Synonyms

unlawful
illegitimate
prohibited
forbidden

Antonyms

legal
permissible
lawful

Common mistakes

Confused with 'unlawful', which can have a broader meaning.
Using 'illegal' to describe moral wrongs instead of legal ones.
Misusing as a noun instead of an adjective, e.g., saying 'the illegal is punishable' instead of 'the act is illegal'.