law of variable proportions

The law of variable proportions states that when at least one factor of production is fixed while the other is variable, the marginal product of the variable factor will eventually diminish as more quantities of it are employed. This law is applicable to production processes that use two or more factors of production, such as labor and materials. As more of one factor is used, eventually its marginal product begins to diminish and the overall output eventually reaches a maximum level. This law demonstrates the diminishing returns associated with increasing the use of one factor of production while other, fixed factors remain the same.