Noun au has 2 senses
  1. gold, Au, atomic number 79 - 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
    --1 is a kind of noble metal
    --1 is a substance of
     dental gold; sylvanite, graphic tellurium; gold foil; gold leaf; gold
    --1 has particulars: gold dust; green gold; guinea gold
  2. Astronomical Unit, AU - 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)
    --2 is a kind of astronomy unit
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