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)
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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. 現在許多大氣球中充的是氦氣。