helium

a very light colorless element that is one of the six inert gasses; the most difficult gas to liquefy; occurs in economically extractable amounts in certain natural gases (as those found in Texas and Kansas)

6種の希ガスの1つである非常に軽い無色の気体元素；最も液化しにくい気体；（テキサス州やカンザス州で見られるような）特定の天然ガスに経済的に抽出可能な量が含まれる