upper jaw Definition

jaw

either of two complex cartilaginous or bony structures in most vertebrates that border the mouth, support the soft parts enclosing it, and usually bear teeth on their oral margin:

an upper structure more or less firmly fused with the skull —called also upper jaw, maxilla

a lower structure that consists of a single bone or of completely fused bones and that is hinged, movable, and articulated by a pair of condyles with the temporal bone of either side —called also inferior maxillary bone, lower jaw, mandible