What is the definition of a ¾ crown?

A ¾ crown on a premolar or molar covers the occlusal and 3 lateral surfaces (generally the mesial, lingual, and distal surfaces) preserving the facial surface. The restoration extends below the height of contour of either the facial or lingual surface. A ¾ crown on an anterior tooth, involves either the mesial, facial and distal surfaces or the mesial, lingual, and distal surfaces. See D2983 for a ¾ porcelain crown (more aggressive prep) versus a porcelain veneer D2962.