Physiological wearing away of tooth, due to tooth to tooth contact is known as:
Attrition 
Attrition may be defined as the physiological wearing away of a tooth surface as a result of tooth-to-tooth contact as in mastication. This occurs only on the occlusal, incisal, and proximal surfaces of teeth not on other surfaces. This phenomenon is physiologic rather than pathologic and it is associated with the aging process. The older a person becomes, the more attrition is exhibited.
Attrition commences at the time, the contact or occlusion occurs between adjacent or opposing teeth. It may be seen in the deciduous dentition as well as in the permanent, but severe attrition is seldom seen in primary teeth because they are not retained for any great period of time.
Reference: Shafer’s Textbook of ORAL PATHOLOGY Eighth Edition page no 648
Attrition
Abrasion
Abfraction
Dental erosion