Deutsch: Flüssigkeit / Español: Líquido / Português: Líquido / Français: Liquide / Italiano: Liquido
Liquid is one of the four fundamental states of matter (the others being solid, gas, and plasma), and is the only state with a definite volume but no fixed shape. A liquid is made up of tiny vibrating particles of matter, such as atoms and molecules, held together by intermolecular bonds. Water is, by far, the most common liquid on Earth. Like a gas, a liquid is able to flow and take the shape of a container. Some liquids resist compression, while others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly constant density.

In the environmental context, "liquid" refers to a substance that has a consistent volume but can change its shape to conform to the shape of its container. Here are some examples:

1. Water: This is the most common liquid found in the environment. It is essential for life and is found in rivers, lakes, oceans, and groundwater.

2. Oil: This is a liquid that is commonly used for energy and transportation. It is found in underground reservoirs and can be extracted through drilling.

3. Mercury: This is a toxic liquid metal that is found naturally in the environment but can also be released through human activities such as coal burning and mining.

4. Acid rain: This is a liquid precipitation that has a lower pH than normal rain due to the presence of pollutants such as sulfur dioxide and nitrogen oxide.

Other terms that are similar to "liquid" in the environmental context include:

1. Fluid: This refers to any substance that can flow and has no fixed shape, including both liquids and gases.

2. Solvent: This refers to a liquid that is capable of dissolving another substance, such as water or alcohol.

3. Viscous: This refers to a liquid that is thick and sticky, such as molasses or honey.

4. Aqueous: This refers to a solution in which water is the solvent, such as seawater or a sugar solution.