A hinge is a mechanical device that connects two solid objects, allowing a relative motion between them. Hinges may be made of flexible material or of moving components. In biology, many joints function as hinges.

There are three main types of door hinges:

• Butt/Mortise Hinges, usually in threes, which are inset into the door and frame
• Continuous Hinges, which run the entire length of the door
• Pivot Hinges which pivot in openings in the floor and the top of the door frame