ChoosingaDictionary
Dictionaries range broadly in purpose, size, and price; and choosing one is a very personal decision. The best advice is to make note of the things you and your family look up in a dictionary over a few weeks' time, and then go to a comprehensive bookstore to make the choice. Here are a few things to look for in making your selection.
Size
Big, complete (unabridged) dictionaries are expensive and take a lot of room in your office or home. They are also difficult for children to use because they are bulky, and it takes longer to look something up because new readers' alphabetizing skills are incomplete. An unabridged dictionary on the coffee table might impress your friends; but unless you use a dictionary on a daily basis, it probably is not a good buy. Perhaps you should look at smaller "college" dictionaries.
Pronunciation guide
Many people use a dictionary to help them pronounce new words. (One caller to the hot line saw an "etagere" advertised for sale, knew what it was and wanted one, but didn't want to call the seller without knowing how to pronounce the word.)
The pronunciation guide should be complete but not contain a lot of unfamiliar symbols that require continual cross-checking--especially with the vowels. The English vowel system is complex because we use one letter to spell many different sounds. For example, the letter A has three different sounds in the words at, age, and art. The job for the dictionary makers is to find three common symbols to represent the different pronunciations.
Examples
Sample sentences showing common uses of words are very helpful, both in clarifying the meaning and helping the reader remember the word. The words in the sentences should not be any more difficult than the target word, however, or the reader is sent off on a frustrating chase through the dictionary. In the words of technology, "A good dictionary should be user-friendly."
Usage Notes
Many dictionaries comment on the usage of words in different types of situations. Many of the old dictionaries contained only the standard accepted usages. "Ain't" was not to be found and teachers could correct their charges by saying, "Ain't isn't in the dictionary." Imagine the teachers' dismay when dictionaries started including such forms! The dictionaries do comment on the usage--non-standard, colloquial, regionalism are some of the terms used to let readers make their own decisions as to whether they want to use the term.
One final comment--forms of speech change much more rapidly than written forms; and many spoken items never make it to the written language (slang, for example). For this reason, you will need to buy several dictionaries during your reading life. Find one that you like, and consider its new editions when it's time for a new one.