In materials science, wear is the erosion of material suffered by a solid surface by the action of another surface. It is related to interactions between surfaces and more specifically to the removal of material from a surface as a result of mechanical action.[1]​ The need for mechanical action, in the form of contact due to relative motion, is an important distinction between mechanical wear and any other process with similar results.[2]​.

Under normal operating parameters, changes in properties during use normally occur in three different stages, which are:

• - Primary or early stage, where the speed of change can be high.

• - Secondary or middle-aged phase where the rate of wear remains relatively constant. Most component lifes are measured in this phase.

• - Tertiary or advanced-age phase, where a high degree of aging results in rapid failure.

The study of wear processes is part of the science of tribology. The complex nature of wear has delayed its study and has directed it towards specific wear mechanisms or processes.[3]​ Some specific wear mechanisms (or processes) are:

1. • Adhesive wear.

2. • Abrasive wear.

3. • Superficial fatigue.

4. • Wear due to friction.

5. • Erosive wear.

In addition to the above, there are other types of wear commonly found in specialized literature such as; Impact wear, cavitation wear, diffusive wear and corrosive wear.

• - Rheology.

• - Abrasion.

• - Tribometer") — equipment used to measure wear.

• - Obsolescence.

• - Bowden, Tabor: Friction and Lubrication of Solids (Oxford:Clarendon Press 1950).

• - Kleis I. and Kulu P.: Solid Particle Erosion. Springer-Verlag, London, 2008, 206 pp.

• - Zum Gahr K.-H.: Microstructure and wear of materials, Elsevier, Amsterdam, 1987, 560 S.

• - Jones J. R.:Lubrication, Friction, and Wear, NASA-SP-8063, 1971, 75 pp.