The Probert Encyclopaedia of Ships

DISPLACEMENT

Displacement is the size of a ship as measured by the actual weight of water which it displaces when afloat. When a ship is launched, part of the ship's hull is in the water, partly submerged. This part of the ship dislodges or displaces a quantity of water, the weight of which water is used as a relative measurement of the size of the ship, known as the displacement. Larger ships displace more water than smaller ships, and hence a ship's displacement is a useful indication of the ship's size.
Research Displacement