Unit weight is

• A. the weight of a material occupying a volume
• B. the weight per square meter
• C. weight after compaction
• D. density

Answer: (A)

Unit weight is the weight per unit volume of a material. That means it tells you how much weight is contained in a given volume, typically expressed as kN/m^3 or lb/ft^3. This is exactly what the option describing the weight of a material occupying a volume conveys. It’s different from density, which is mass per volume, and it’s different from weight per area, which would be a surface load. For example, if 1 m^3 of soil weighs 19.6 kN, its unit weight is 19.6 kN/m^3. Also, compaction can change the unit weight, but the concept itself is still weight per volume, not weight after a specific process.