Gasous

Gasous is not a standard scientific term; the correct adjective is gaseous. In contemporary usage, gaseous describes matter in the gaseous state, one of the fundamental states of matter alongside solid, liquid, and plasma.

The gaseous state is characterized by indefinite shape and indefinite volume. Gases expand to fill their container and are typically less dense than solids or liquids. The molecules in a gas move rapidly and collide with each other and with container walls in elastic collisions. Because of this high kinetic energy, gases are highly compressible and can mix thoroughly with other gases to form homogeneous or nearly uniform compositions.

Gas behavior is described with principles such as the kinetic theory and gas laws. The ideal gas law, PV = nRT, provides a useful approximation for many gases under a range of conditions, linking pressure, volume, temperature, and quantity. Real gases exhibit deviations at high pressures or very low temperatures, where interactions between molecules become significant. Gas mixtures, such as air, are common and can be analyzed as combinations of individual gas components.

Common examples of gases include nitrogen, oxygen, carbon dioxide, hydrogen, and noble gases like helium and neon. Gaseous substances play essential roles in science, industry, medicine, and everyday life, from respiration and combustion to chemical synthesis and refrigeration.

Etymology notes: the term gas originates from early modern chemistry, while the adjective gaseous is formed from gas plus the suffix -ous. The nonstandard form gasous may appear as a misspelling or historical variant in some texts.