Criminal is a term with multiple meanings in English:
1. As a noun: A person who has committed a crime.
2. As an adjective: Relating to crime or illegal activities.
3. In legal context: Pertaining to criminal law as opposed to civil law.
4. Colloquially: Used to describe something shockingly bad or unfair.
Example sentences:
"The criminal was sentenced to 10 years in prison."
"Criminal behavior will not be tolerated in this community."
"It's criminal how much they charge for basic healthcare."