Ship's constant refers to the difference between the actual displacement of a ship in its light ship condition and the light ship weight recorded in ship's documentation. It reflects the irremovable additional weight accumulated during ship operation, including:
1. Attachments on the hull (such as shells, rust)
2. Residual oily sewage (bilge oil residue, remaining oil in the dirty oil tank)
3. Spare parts (cables, paint, tools, etc.)
4. Weight increase due to ship modification or maintenance