A state of matter in which a substance has no fixed shape and expands to fill its container (e.g., air, hydrogen); contrasted with liquids and solids.
空気は主に窒素と酸素からなる気体だ。
Air is primarily a gas composed of nitrogen and oxygen.
気体は容器の形に従って広がるという性質がある。
Gases have the property of expanding to take the shape of their container.
物質の三態は固体、液体、気体で表される。
The three states of matter are solid, liquid, and gas.