気体
きたい · kitai · JLPT N3 · noun
gas
💨🎈 気体 = air (気) + body (体): matter whose body is air
気 means air, spirit or energy, and 体 means body or substance. A gas is a substance in its air form. The same 体 shows up in 液体 (liquid) and 固体 (solid), so the three states of matter all end in 体.