See also Solid
Liquid is a state of matter in which the constituent molecules are not constrained in their relative location to each other. In the way it flows, a liquid behaves similarly to a gas. Unlike a gas it occupies a nearly fixed volume, regardless of the pressure. Where in contact with a gas, a liquid will be bounded by a well-defined surface, whose strength is described by a property called surface tension. Surface tension is responsible for most of the phenomena we associate with liquids, including wetting to surfaces, and the tendency of small droplets to form spheres.
Water is a well known liquid at room temperature and pressure.
A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a nearly constant volume independent of pressure. It 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.
The density of a liquid is usually close to that of a solid, and much higher than that of a gas. Therefore, liquid and solid are both termed condensed matter. On the other hand, as liquids and gases share the ability to flow, they are both called fluids.
A liquid is made up of tiny vibrating particles of matter, such as atoms, held together by intermolecular bonds. Like a gas, a liquid is able to flow and take the shape of a container. Unlike a gas, a liquid maintains a fairly constant density and does not disperse to fill every space of a container.
Although liquid water is abundant on Earth, this state of matter is actually the least common in the known universe, because liquids require a relatively narrow temperature/pressure range to exist. Most known matter in the universe is either gas (as interstellar clouds) or plasma (as stars).