Precarium is a specie of commodatum where the bailor can demand the return of the thing at will. This is a contractual relationship. (Art. 1947) The original word for precarium is precarious which means “unstable.”
Precarium is allowed when: (1) NO STIPULATION – there is no duration of the contract or the purpose of the loan is not stipulated; or (2) TOLERANCE – if the use of the thing is merely tolerated by the owner. (Art. 1947); or (3) INGRATITUDE – if the bailee commits any acts of ingratitude under Article 765. (Art. 1948)
But if there’s a period agreed upon in which the bailee can use the thing, the bailor cannot exercise the rights under precarium or demand the return at will until the expiration of the contract.
Except if the bailor has an urgent need, the bailor can demand the return even before the period of use expires. The period is not terminated but is only deemed suspended.