(the Trinity) according to Christian theology, the unity of Father, Son, and Holy Spirit as three persons in one Godhead
a group of three closely related people or things
Inside the rose-tinted, air-conditioned, environment-proof bulk reigned the modern architectural trinity, cleanliness, spaciousness and luminosity — Richard G Stern
[from early French trinité, from Latin trinitas the state of being threefold, from trinus threefold, from tres three]