a soft yellow malleable ductile (trivalent and univalent) metallic element; occurs mainly as nuggets in rocks and alluvial deposits; does not react with most chemicals but is attacked by chlorine and aqua regia
a unit of length used for distances within the solar system; equal to the mean distance between the Earth and the Sun (approximately 93 million miles or 150 million kilometers)
AU的用法和樣例：
例句
It's my first week here so I'm not yet au fait with the system. 我剛來不到一個星期，對這裡的制度還不太熟悉。
Au revoir, see you again next year! 再見，明年見！
We've got a German au pair for six months. 我們找到了一個可以干六個月的德國換工。
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