This is the 10325th most frequent French word.
interdire
To prohibit or forbid.
The word 'interdit' is used here as an adjective, meaning 'forbidden', to indicate prohibition.
Il est interdit de fumer ici.
It is forbidden to smoke here.
The word 'interdit' is used as a verb ('interdire') in third-person singular form, meaning 'prohibits', to show that a restriction is enacted.
L'école interdit l'usage des téléphones en classe.
The school prohibits the use of phones in class.
The word 'interdire' is used as an infinitive verb, meaning 'to forbid'. It is linked with 'à quelqu'un' (to someone) indicating the action of prohibiting an action to someone.