hollowness
  凹窩,空曠,空虛
  Hol·low·ness, n.
  1. State of being hollow.
  2. Insincerity; unsoundness; treachery.
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  hollowness
       n 1: the state of being hollow: having an empty space within
            [ant: solidity]
       2: the property of having a sunken area