Tonnage refers to the weight or capacity of a ship or the amount of cargo a ship can carry. Some synonyms for tonnage include load, cargo capacity, volume, weight, and freight. Other synonyms for tonnage include displacement, tonnage rating, and deadweight tonnage, which refers to the total weight a ship can carry without sinking. In the shipping industry, tonnage is often measured in metric tons or long tons. Regardless of the units used, tonnage is an important factor in determining a ship's efficiency and profitability. Consequently, ship owners and operators pay close attention to tonnage and strive to increase it whenever possible.