A strong wood joint. The mortise is a hole cut into one piece of wood and the tenon is the piece that goes into it, usually at right angles. It is then glued and can also be screwed.

Simple joinery where the mortise is a cavity into a piece of wood receiving a tenon to create a solid stable angle of a table.

A specific joining technique. The mortise (groove or slot) is cut into a piece of wood. The joint is made when an opposing piece cut with a tenon (a collared protrusion) is slipped into the mortise.

During Antiquity, this was a common way to fasten hull planks to each other, edge to edge, by inserting a multitude of plugs into adjoining planks. It was practiced until the end of the Roman Empire, often together with the shell-first method.