Select the right kind of dictionary. Bilingual, second language and standard one-language publications provide necessary definitions and tools.
Consider the dictionary's size. Choose a size based on use and features. A smaller size is portable and good for the backpack or pocket, a general dictionary for the office or desk drawer and a large advanced bookshelf volume for the home.
Think of the word level and complexity of definitions that you need. A bookshelf dictionary contains up to 400,000 words, advanced averages 80,000, intermediate around 40,000 and elementary averages 2,000 words.
Decide what features you want. Dictionaries are specialized and vary in content according to maps, pronunciation guides, reference tables, word histories, synonyms and grammar usage.
Compare word definitions across several dictionaries before you buy. Note how the words are defined including added material to determine which one best reflects your purpose and usability.
Choose hardbound, paperback or CD versions. Many publishers offer both paper and digital dictionaries for the same edition.
Determine your price range for the dictionary. They range from a few dollars to thousands of dollars for exhaustive language sets.