accessio (ak-s<<schwa>>sh-ee-oh) n.[Latin] Roman law. 1. The doctrine by which
something of lesser size, value, or importance is integrated into something of greater size, value,
“If the identity of one thing (the accessory) is merged and lost in the identity of the other (the
principal), the owner of the principal is the owner of the thing…. There is said to be accessio….
The term is used by some commentators (and, following them, by the French Civil Code) in a
much wider sense to include all cases in which there has been an addition to my right, i.e. in which
the object of my ownership has increased. The owner of an animal therefore acquires ownership of
the young of the animal at birth by accessio, though in physical terms there has been not an
accession but a separation. In this sense accessio includes all the original natural modes except
occupatio and thesauri inventio. And there are other, intermediate, meanings. Since accessio as an
abstract word is not Roman and no clear classification emerges from the texts, no one meaning or
classification can be said to be ‘right,’ but those adopted by the French Civil Code are so wide as
to be almost meaningless.” Barry Nicholas, An Introduction to Roman Law 133 & n.1 (1962).
2.ACCESSION(4). [Blacks Law 8th]