What is a good dictionary?
With the advent of information technology, the number and types of dictionaries have increased. In addition, due to the convenience of using IT in dictionary making demands on the quality of dictionaries have also become higher but advertising and some recommendations might tempt people into making wrong decisions. Consequently it is not an easy task to make the right decision in the choice of a dictionary in the present market jungle. A rule of thumb is: if you decide to buy a dictionary at a bookshop, compare a couple of entries of some key words and find out for yourself which dictionary is better for you. In addition to some guidelines the design, layout, fonts play an important role.
What was once Chinese or Arabic leadership in lexicography has been taken over by the British tradition since Murray and the American since Webster. OED (The formidable Oxford English Dictionary) is perhaps the most comprehensive and scientific dictionary in the world. In addition, English dictionary making is facing the challenge of recording the inventory of a language which exceeds the vocabulary of all other European languages put together.

Types of dictionaries
There are different types of dictionaries
1. Translation dictionaries
2. Historical/etymological dictionaries
3. Specialist dictionaries as for example: a dictionary of collocations, psychological terms...
4. General monolingual dictionaries

Monolingual dictionaries
Generally speaking monolingual dictionaries have a lot of advantages over translation dictionaries if the objective is not translation.
British and American dictionaries
There are a variety of very good dictionaries on the market. Those dominant are either British or American. So it depends on your interest. In a sense you have always to make a compromise depending upon price, weight, number of entries

British dictionaries:
1. Oxford
2. Cambridge
3. Longmann
4. MacMillan
5. Collins
6. Penguin

American dictionaries
1. Webster
2. Random House
3. American Heritage

Criteria of a good dictionary
In addition to basic information which all dictionaries are committed to give like meaning and pronunciation a good dictionary is supposed to:

1. give collocations or partnerships
2. make you aware of False Friends
3. give idioms and phrasal expressions
4. give guidance on confusing words
5. give you binomials
6. give at least AmE and BE vocabulary differences
6. use defining vocabulary not exceeding 3000 words and give the list at the end of the dictionary.
7. give abbreviations and acronyms

1. AmE and BE and other varieties
2. provide a CD with audio files

Visual aids
1. use pictures, graphs, tables
3. come with an optical disk like a CD or a DVD containing multimedia files: (audio files, video files, picture files, text files and even program files).
4. type the entries in a different colour i.e. entries are highlighted and more convenient to read.
5. use labels as for example: formal/informal, countable/uncountable....

1. The size: not to be too thick but also not too thin
2. Format: nice to feel and thumb
3. organize entries according to frequency and usefulness

Notes or info boxes
1. give help on usage
2. provide Cultural notes
3. give additional information
4. provide encyclopedic extra pages on some important aspects of language. For example topics can vary from metaphor, business language, computer language, pragmatics, business correspondence, writing skills...

1. not to be too expensive