Definition of permanent hardness in English:

permanent hardness

Line breaks: per¦man|ent hard|ness

noun

[mass noun]
  • The presence in water of mineral salts (chiefly calcium sulphate) that are not removed by boiling.

Get more from Oxford Dictionaries

Subscribe to remove adverts and access premium resources

Word of the day coloratura
Pronunciation: ˌkɒlərəˈtjʊərə
noun
elaborate ornamentation of a vocal melody