Définition
To naturalise a foreigner is to grant him the status of full French citizenship. Naturalisation is a way of acquiring French nationality which is not automatic. It is made by decision of the public authority (decree) and is granted to a foreigner under certain conditions (residence in France, integration, knowledge of the French language, morality, etc.).
Remarque
See https://www.service-public.fr/particuliers/vosdroits/F2213