(Latin: advocatio, legal assistance)
In English law the right of presenting one to a vacant ecclesiastical benefice; so called because the patron advocates or defends the claims of the one presented.
Originally the right of presentation was conferred upon a person building or endowing a church, but in time this right became annexed to the manor and thus passed from owner to owner.
It was then known as advowson appendant.
If separated from the estate it was the advowson in gross.
Advowsons are either presentative or collative; collative when the bishop himself is the patron, and presentative when the bishop installs one duly presented by another.
New Catholic Dictionary