According to the general definition, bulk material is a powdery, grainy to granular-shaped or also lumpy mixture that is present in a pourable form. This means that it can be moved in a coherent form.  

The principal bulk material parameters for the design of bulk material systems are the particle size and the particle size distribution, the particle density and the bulk density, the moisture, the temperature as well as the surface condition of the individual grain and the specific hardness of the grain of the respective bulk material.