Step 1: Understanding the Concept:
Physical and bulk properties of agricultural grains dictate storage bin design and grain handling operations.
Step 2: Detailed Explanation:
Density (specifically bulk density or test weight) is defined as the mass (or weight) of granular grain material occupying a unit volume under specified standard conditions:
\[\text{Density} = \frac{\text{Weight}}{\text{Volume}}\]
Specific gravity is a dimensionless ratio of density to the density of water, while mass is the absolute quantity of matter.
Step 3: Final Answer:
Therefore, weight per unit volume of grain is known as density.