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1. A hinged part; a separately movable division of a folding or sliding door.
2. One of a pair of doors or windows.
McGraw-Hill Dictionary of Architecture and Construction
1. The distance from the edge of the door, to the center of the bore hole in the door
Door Hardware Institute
1. A mechanism housed within door locks that contains the tumbler and keyway, into which a key is inserted to operate the lock.
Homestead Commercial Door Glossary