A proper design includes the prediction of circumstances under which failure is likely to occur. In the most general terms, failure refers to any action that causes the member of the structure or machine to cease to function satisfactorily. The strength, stiffness, and stability of various load-carrying members are possible types or modes of failure. Failure may also be associated with poor appearance, poor adaptability to new demands, or other considerations not directly related to the ability of the structure to carry a load. Important variables associated with the failure include the type of material, the configuration and rate of loading, the shape and surface peculiarities, and the operational environment.