acid·i·ty /əˈsɪdəti, æ-/
  酸味,酸性
  acid·i·ty /əˈsɪdətɪ, æ-/ 名詞
  酸度
  A·cid·i·ty n.  The quality of being sour; sourness; tartness; sharpness to the taste; as, the acidity of lemon juice.
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  acidity
       n 1: the property of being acidic [syn: sourness, sour]
       2: the taste experience when something acidic is taken into the
          mouth [syn: acidulousness]
       3: pH values below 7 [ant: alkalinity]