Dictionaries and thesauruses are reference books for words. But what's the difference between them? When do we use a dictionary and when do we use a thesaurus?


A dictionary is a list of words arranged alphabetically, and for each word you can see:

  • definition : the meaning or meanings of the word, often with example sentences
  • part of speech: whether the word is a noun, verb, adjective etc
  • correct spelling: the exact spelling and any possible alternatives
  • pronunciation : how to say the word
  • etymology: the origin of the word (did it come from Latin, for example?)

Here is a simple example of a dictionary  entry for the noun "dog":

dog (noun):  a domesticated, meat-eating animal that usually has a long snout, excellent sense of smell, and a barking or howling voice

When you want to know what a word means, you look in a dictionary.


A thesaurus is a list of words arranged in conceptual groups or alphabetically, and for each word you can see:

  • similar words: a number of words that have nearly the same meaning or the same meaning (synonym)
  • opposite words: one or two words that have the opposite meaning (antonym) or nearly opposite meaning

Here is a simple example of a thesaurus  entry for the noun "dog":

dog (noun):  hound, canine, mongrel, tyke; bitch, pup, puppy, whelp; doggy, mutt

When you don't know the exact word you that want, you look in a thesaurus.


  • A thesaurus does¬†not ¬†give the meaning of words.
  • A thesaurus does not always include antonyms.
  • The plural of thesaurus is "thesauri" or "thesauruses".

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