From French acidité, from Latin aciditātem, accusative singular of aciditās (“sourness, acidity”), from acidus (“sour, acid”). Equivalent to acid +‎ -ity.

• (UK) IPA^(key): /əˈsɪdɪti/

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acidity (countable and uncountable, plural acidities)

1. The quality or state of being acid.
2. Sourness; tartness; sharpness to the taste.

   the acidity of lemon juice

   Empty stomachs lead to acidity and leave a sour taste in the mouth.

3. (pathology) Excessive acid quality, as in gastric secretions.
4. (figurative) A caustic, sour, biting, or bitter quality.
   • 1912, Arthur Conan Doyle, The Lost World […], London; New York, N.Y.: Hodder and Stoughton, →OCLC:

     "What shall we call it?" he asked. "Why should you not take the chance of perpetuating your own name?" said Summerlee, with his usual touch of acidity.

   • 1913, Arthur Conan Doyle, “The Time of Death”, in The Poison Belt […], London; New York, N.Y.: Hodder and Stoughton, →OCLC, page 60:

     It was a brave, good speech, a speech from that staunch and strong spirit which lay behind all the acidities and angularities of the old zoologist.

• alkalinity
• basicity

• adicity