General definition of machine elements. Standardization and standard numbers. Surface roughness. Tolerances. Temperature influence on contiguous changes. Measurement chains. Fundamental mechanical characteristics of machine materials. Load of machine elements (types, origin, classification, and application in time). Behaviour of machine elements under load (tension, stress and strain). Ideal and real materials. Stress concentration. Static strength. Material wear. Dynamic persistence, permanent or temporary limitations, in constant and alternating load regimes. Influences on dynamic persistence of machine elements. Working, critical allowed and calculated stresses. Safety of machine elements. Screw relations. Group screw relations. Thread transmitters. Rivets. Mechanical transmitters. Friction pairs.