What is a dictionary used for?

I need to know other uses of the dictionary beside spelling words.What is a dictionary used for?
dic鈰卼ion鈰卆r鈰厃鈥傗€?藞d瑟k蕛蓹藢n蓻ri/ Show Spelled Pronunciation [dik-shuh-ner-ee]

鈥搉oun, plural -ar鈰卛es. 1. a book containing a selection of the words of a language, usually arranged alphabetically, giving information about their meanings, pronunciations, etymologies, inflected forms, etc., expressed in either the same or another language; lexicon; glossary: a dictionary of English; a Japanese-English dictionary.

2. a book giving information on particular subjects or on a particular class of words, names, or facts, usually arranged alphabetically: a biographical dictionary; a dictionary of mathematics.

3. Computers. a. a list of codes, terms, keys, etc., and their meanings, used by a computer program or system.

b. a list of words used by a word-processing program as the standard against which to check the spelling of text entered.What is a dictionary used for?
To look up words you don't know the meaning of.