criminel

In a sentence

• Le criminel a été arrêté par la police.

  The criminal was arrested by the police.

  Here, 'criminel' is used as a noun to describe someone who has committed a crime.

• Son comportement criminel est préoccupant.

  His criminal behavior is concerning.

  In this sentence, 'criminel' functions as an adjective describing the behavior.

• Elle a dû faire face à des accusations criminelles.

  She had to face criminal charges.

  'Criminelles' is an adjectival form agreeing in gender and number with 'accusations,' referring to the nature of the charges as related to criminal law.