Liquid refers to one of the four fundamental states of matter. It has no fixed shape but occupies a definite volume and possesses the ability to flow and rotate.

Liquid bulk refers to goods that are in a fluid or semi-fluid state. These goods include oil, petroleum products, vegetable oils, and liquid chemical raw materials. Crude oil and refined oil transported in large quantities through ports fall under the category of flammable liquids. The liquid chemical raw materials that are commonly transported via waterways mainly include acids (such as sulfuric acid, acetic acid, hydrochloric acid, etc.), bases (such as caustic soda), alcohols (such as methanol, ethanol), and aromatic compounds (such as phenol). Most liquid chemical raw materials are corrosive and, in terms of flammability and explosiveness, are generally less hazardous than petroleum chemical products.