A key, in mechanical engineering, is a machine element used to connect a rotating machine element to a shaft. These Keys covers the entire range of basic and applied aspects of characterization and the synthesis , application, modelling and processing of advanced materials for engineering. The key prevents undesirable movement between the two parts and may enable increased torque. Keyway are used for a key to function, which is a slot in which the key fits to a shaft on the rotating machine element. A keyed join, which whole system is called, may allow relative movement between the parts when designed to acomidate.