This chapter focuses on fundamental principles involved in lubrication and wear. Because this chapter addresses basic design principles of tribological processes in lubrication and wear testing, numerous equations are utilized. The applicability of these relationships to tribological testing is also discussed. The structure of this chapter is to first address basic principles involved in friction. After friction, wear, and principles of fluid lubrication are discussed. The last section of this chapter provides an overview of additive chemistry in the formulation of lubricants.