In the long run, all production factors are "variable." This means that in the long run, a firm can adjust all of its production inputs, including labor, capital, and technology, to change the scale of its operations. In the short run, some inputs may be fixed, such as the size of the factory, which can only be changed in the long run. But in the long run, all inputs can be varied to optimize production and increase efficiency. The ability to adjust all inputs in the long run is what distinguishes the long run from the short run in the theory of production.