Latin. n. Approach, increase, bonus, accessory, attack, onset (fever, rage), fit. A doctrine that creates a presumption of ownership from the act of integrating something of lesser size, value, or importance into something of greater size, value, or importance.
If the identity of the accessory (thing) is merged and lost in the identity of the principal (another thing), the owner of the principal is the owner of the resulting thing created by the merger.The right of an owner of personal property to the personal property of another which is incorporated into or united with his property. The rights which an owner of real or personal property has to any increase in property from any cause, natural or artificial. See Accession.
In French Civil Code this includes all cases in which there has been an addition to a right. Thus an owner of an animal acquires ownership of the young of that animal at birth. This includes all the original natural modes except occupatio and thesauri inventio.