What is the difference between a dictionary, a lexicon, and a glossary?

These reference books have slightly different denotations. A glossary is a specialized vocabulary with definitions but does not provide other information about the words. A glossary may also be called a vocabulary. A lexicon is generally an alphabetically-arranged list of words with their definitions, but the term does not imply that other information about the words is included. However, a lexicon can be used to mean glossary or dictionary, in which case it would contain what each of those words' definitions entail. Lexicon is considered by some to be a more formal word for dictionary. A dictionary is a reference book consisting of an alphabetically-arranged list of words with their definitions, as well as any or all of these: forms (spellings), pronunciations, functions (parts of speech), etymologies, and syntactical and idiomatic uses. So, dictionary is usually reserved for the more comprehensive type of word book. Lexicon's etymology is Greek, while dictionary's is Latin.

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