Matrimony is a formal word most often used in documents and in the words of the ceremony. When a couple ties the knot, they are engaging in matrimony. The actual wedding celebration can be described as matrimony, and the state of being married also can be described as matrimony. Patrimony and matrimony are a right, a status or tangible asset inherited from a ancestor. Though the Latin elements matri– and patri– are derived from the words for mother and father, “matrimony” and “patrimony” are not the feminine and masculine versions, like “matriarchy” and “patriarchy.” The word “matrimony” never really had to do with property handed down by a mother, and “patriarchy” never meant the state of marriage. “-mony,” as the Oxford English Dictionary explains, occurs “in essentially abstract nouns mainly denoting a state, condition, or action.”
To the Romans, matrimonium meant the state of being married. But patrimonium, says the OED, meant the “property of the head of a household, personal estate, fortune, private chest of the Roman emperors.” And in post-classical Latin it also meant the “estate of the church.”