Definition -
(1) A collection of concepts or words that has been arranged according to sense.
(2) In the USA the term also denotes a dictionary of synonyms and antonyms.

Example -
Roget's Thesaurus

Etymology -
The word derives via Latin from the Greek thesauros, a treasury or storehouse (from the Greek tithenai, to put or place).

Oxford English Dictionary -
Its first citation in this sense is from 1852:
"Thesaurus of English Words and Phrases classified and arranged [etc.]."
(Roget (title))

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