In the broad sense, Just-In-Time is an approach to achieving excellence in a manufacturing company based on continuing elimination of waste and consistent improvement in productivity. Waste is then defined as those things which do not add value to the product. Waste can be divided into two categories: necessary and unnecessary. Unnecessary waste should be eliminated, and necessary waste should be made unnecessary so that it too can be eliminated.

In the narrow (and less correct) sense, Just-In-Time is considered by some as a production and logistics method designed to result in minimum inventory by having material arrive at each operation just in time to be used.