Dictionaries

Five things you need to know

The best dictionaries today are FANTASTIC - very powerful learning tools. They help you to build up your vocabulary in a completely different way from the old dictionaries. They can also teach you about writing and many other things. Most of the best are published by these companies: Cambridge, Oxford, Collins, Macmillan and Longman.
The dictionary in your mobile phone is probably old-fashioned and poor quality: new technology but old (and bad) content. Most hand-held electronic translators have the same problem. You can now get excellent electronic dictionaries and there are links to some below.
A translating dictionary is useful but it is not enough to help you develop a better vocabulary - and learn how to use the new words. You need BOTH a translating dictionary AND an English-English one.
The best dictionaries are available both in electronic and book form. The cheapest way to buy them is to get the book and CD together. If you are going to study English seriously, it's helpful to have the book too. You may be able to download the dictionary without buying the book, but it's not always cheaper.
Some of the best dictionaries are now available online - free (see links below). They have many excellent EXTRA features, though. You only get these extras when you buy the dictionary. There are more extra features only on the CD-ROM.

Oxford Advanced Learner's Dictionary with CD-ROM Click "see inside" and choose Presentation. Look at the iWriter (on the CD) - very helpful.
Help choosing Oxford dictionaries This page helps you choose. You can also see details of each dictionary - and a demo of how its software works.
Cambridge Advanced Learner's Dictionary with CD-ROM. Click "view inside".
Macmillan Study Dictionary with CD-ROM - for university students. To see other Macmillan dictionaries, clear here and then click "Dictionaries" for a demonstration of how they work.
Oxford Student's Dictionary of English with CD-ROM - for university students. Click "see inside" and look at the sample pages.
The Longman Dictionary of Contemporary English This includes free software which tests how well you can use a word, then remembers that and tests you again later.

The Longman Language Activator This helps you choose the right word when you are writing by taking you from a basic concept, such as cheap, and helping you identify that reasonable is the word you need to describe your products (not cheap - which sometimes means "cheap but bad quality").

Cambridge dictionaries for your phone There's a long list of good dictionaries here, including English-Chinese.
Oxford Dictionary apps
Collins Dictionaries for iPhones and iPads. Excellent English-English dictionaries - and excellent translating dictionaries (Mandarin, Polish, Spanish, French, German, Italian).

Oxford including Arabic, Catalan, Czech, Farsi, French, Greek, Hungarian, Italian, Korean, Polish, Portuguese, Russian, Serbian, Spanish, Thai, Turkish and Vietnamese dictionaries. Some are study dictionaries, some are only pocket dictionaries. There are Picture Dictionaries for many of these languages at this page.
Longman have a good English-Japanese study dictionary.

Oxford Advanced Learner's Dictionary
Macmillan Dictionary
Cambridge Learners' Dictionaries Online. You can choose which Cambridge dictionary you want - just use the pull-down menu at the top left. There are several dictionaries available - including a phrasal verbs dictionary, Advanced Learners' Dictionary and Elementary (Essential) dictionary.
Free online translations