Density is defined as:

Density is defined as the mass of a substance divided by its volume. In the context of this question, the concept of weight can also relate to density because weight is essentially the force exerted by gravity on mass. Thus, although specific terms used in the definition may vary, understanding density in relation to weight can still apply, particularly since weight can be expressed as mass times the gravitational acceleration.

When density is expressed using weight, it can be represented as weight divided by volume. This understanding allows for practical application in various fields, including HVAC, where the density of a refrigerant or air affects system performance, efficiency, and design considerations.

Other responses do not accurately reflect the definition of density. For instance, mass divided by temperature does not yield a density measurement, and weight multiplied by volume would not produce a meaningful physical quantity related to density. Mass divided by weight would not be a correct equation for density either, as it would invert the concept. Thus, understanding the correct relationship of weight and volume leads to the acceptance of the definition associated with density.