• difference between the lightweight and loaded displacement¹⁾
• Deadweight of a ship varies with the draught.²⁾ The deeper the ship is in the water, the more weight it can carry—hence, its deadweight increases.
• a measure of a ship's capacity and does not include the weight of the ship itself

Deadweight tonnage (also known as deadweight; abbreviated to DWT, D.W.T., d.w.t., or dwt) or tons deadweight (DWT) is a measure of how much weight a ship can carry. It is the sum of the weights of cargo, fuel, fresh water, ballast water, provisions, passengers, and crew.(https://archive.ph/4omXC#selection-1457.0-1525.3)

• When describing a ship it is usual to use its summer deadweight (sdwt).³⁾