a type of joint or juncture used to connect two pieces of material; a mortise (also "mortice") usually is a rectangular cavity in a piece of wood, stone, or other material, shaped to receive a tenon; conversely, a tenon is a projection on the piece to be attached, shaped to fit into the mortise.
This joint is often used to connect perpendicular pieces of wood. The tenon is a rectangular projection on the end of one piece. The tenon slides into the mortise, a corresponding hole in the adjoining piece. Look for the mortise-and-tenon joinery on table and chair bases.