Short run production period and long run production period:

The short run is a period of production during which some factors of production are fixed and some too are variable. The fixed inputs cannot be varied when demand conditions require a change in output. This period varies from firm to firm, depending on the type of production a firm undertakes and the inputs it uses whiles the long run is a period of production within which all inputs are variable. This implies that if demand conditions warrant a change in production all the inputs can be varied to achieve this.