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Alternative forms[edit]



  1. (rare, nonstandard) misconstruction of thesauri or thesauruses; plural form of thesaurus
    • 1965, Pierre A. Rinfret, “Changing Population and Changing Demand”, Financial Analysts Journal, volume 17, number 5, JSTOR 4469254, page 75: 
      In the closing weeks of 1959 and the early weeks of 1960, book dealers must have had a bonanza in selling thesaurusi.
    • 1999, Lynn Tooma; et al., Exploring the Bible, ISBN 0884894649, OL 8194643M, page 49:
      Gather a variety of dictionaries and thesaurusi written for middle-school students as well as adults.
    • 2004, Vincent Mary, “MeSH and Specialized Terminologies”, in MedInfo 2004, ISBN 1586034448, OL 12317592M, page 530:
      UMLS is an integration of several thesaurusi.

Usage notes[edit]

  • This word is incorrectly formed. For masculine nouns in the nominative case of Latin’s second declension (of which thēsaurus is one), -us and are singular and plural endings, respectively; one or the other attaches to the noun’s stem (thesaur-), depending on number: the plural ending does not concatenate as thesaur- + -us + -i = thesaurusi, but rather supplants the singular ending (-us) as thesaur- + -i = thesauri — thus forming the correct Latin nominative plural, which is also valid in English. Alternatively, in English, thesaurus, can be suffixed with the the English plural suffix -es, to form another correct plural form of thesaurus, thesauruses. Thesaurusi is a rare error.