Like peanut butter and jelly, you rarely see the word mortise without its partner, tenon. Mortise and tenon falls under the category of joinery. Like a dovetail, rabbet and mitre, joiners use a mortise and tenon joint when building furniture and constructing cabinetry. The mortise is a hole, groove, or slot into or even through which a tenon passes. Usually the joint is hidden, but, done carefully and properly, this type of joint can be quite decorative, especially when contrasting woods or stains are used. The term mortise may also be used as a verb, as in explaining the act of creating a mortise.
See also: dovetail, joinery