noun (n)

• the property of being acidic(noun.attribute)

  Synonym:
  sour, sourness
  

  source: wordnet30
• the taste experience when something acidic is taken into the mouth(noun.cognition)

  Synonym:
  acidulousness
  

  source: wordnet30
• pH values below 7(noun.attribute)

  Antonym:
  alkalinity
  

  source: wordnet30
• The quality of being sour; sourness; tartness; sharpness to the taste; as, the acidity of lemon juice.(noun)

  source: webster1913