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)
造句
用作名詞(n.)
Helium and neon are inert gases. 氦和氖為惰性氣體。
Most big balloons are now filled with helium. 現(xiàn)在許多大氣球中充的是氦氣。