Mass, volume, and weight all pertain to how heavy something is. However, there are clear differences between the three units. Mass is the measure of the matter within a body. Volume is the quantity of space a body occupies. Weight refers to a body’s relative mass or the quantity of matter contained within that body.
Two different substances with the same volume may have different weight and mass. While mass refers to the amount of matter within an object, weight refers to the pull of gravity on said object and volume refers to how much space that object takes up.