Choosing a dictionary depends on the learner's level, purpose and learning situation. The discussion below considers the relative importance of recency, clarity, defining vocabulary, pronunciation information, corpus evidence and the learner's ability to work independently with English-English reference material.
Choosing a dictionary for English language learning
When buying a dictionary for advanced learners, there is a strong case for considering its publication date, especially if it is to be used for vocational purposes. Fields such as information and communication technology develop rapidly, and new words and expressions can become widely used in a very short time.
At lower levels of proficiency, however, clarity of presentation and the criteria used to select vocabulary are more important than recency. Clear definitions depend partly on the use of a suitable defining vocabulary, so that learners at relatively low levels can understand explanations of word meanings.
Picture dictionaries can be useful in kindergartens and nurseries, but the modern English language coursebook usually contains all the illustration that an elementary learner is likely to need, supplemented by realia in the teaching situation. Maps and wall charts can also be very helpful, particularly when they are displayed where everyone in the class can see them.
At intermediate levels, publishers now offer dictionary materials designed not simply to explain individual words but to encourage learners to activate their language and combine words effectively. These materials are particularly useful in the writing class, where over-reliance on a bilingual dictionary can be counterproductive. You will not get very far in learning written English without access to models of texts written by proficient users of the language. An English-English dictionary is therefore an essential resource for learners who want to perform well in examinations in which written English is assessed.
It is also worth being prepared to leave your dictionary at home when attending language classes that emphasise listening and speaking. Excessive use of a dictionary can delay the development of effective reading strategies, particularly when the texts provided by your teacher are intended to present a reasonable challenge.
The dictionary habit can become unhelpful when learners attempt to look up too many of the words they encounter in reading or listening. Guessing should be encouraged and inference skills developed. Often, a single stressed syllable within an utterance can carry more information than several surrounding unstressed words. Students who try to decode every word from the beginning of a sentence can become distracted by relatively unimportant vocabulary and miss the more significant words towards the end, which may carry the main message.
Do not be surprised, therefore, if your English teacher sometimes bans the use of dictionaries in the classroom. If you are studying in a country where English is the native language, valuable lesson time can be spent listening to English being spoken. Your teacher may not want you reading the language or constantly switching back to your native language, but will instead help you understand meaning through intonation and stress, mime and gesture, or visual aids. Look out for these different ways of drawing attention to the parts of an utterance that contain the main message.
Dictionaries designed specifically for English language learners should provide pronunciation guidance, and it is worth checking that phonetic transcriptions are included for individual words. The International Phonetic Alphabet (IPA) is particularly useful for this purpose. Major ELT publishers also offer dictionaries based on corpus data, providing information about how English is actually used in both speech and writing.
Bilingual dictionaries are generally neither welcomed nor needed in language schools in countries where English is the native language. They can be particularly irritating in multilingual classes where switching to languages other than English is considered bad etiquette and may be a poor learning strategy. There are nevertheless situations in which a bilingual dictionary can be useful, particularly during independent study or when you need to find the precise equivalent of a technical term that is difficult to explain using a simple English defining vocabulary.
Some dictionaries to consider
1. Oxford Elementary Learner's Dictionary
Clear presentation of the meanings and use of essential vocabulary, with additional help in areas of language that may be difficult for elementary learners. It includes a guide to phonetic symbols at the bottom of every page, together with vocabulary-building notes and illustrations.
2. Oxford Wordpower Dictionary
Suitable for learners at intermediate level, with 30,000 references. Example sentences are based on the Oxford Corpus of the English Language and reflect contemporary usage. It provides clear, simple definitions, illustrations of difficult words, and coverage of idioms and phrasal verbs. It is designed to help learners move from a basic survival vocabulary towards greater spoken fluency and confidence with written English. Phonetic spelling and an IPA reference are also provided. The CD-ROM allows learners to search by word or topic.
3. Longman Language Activator
Suitable for learners from upper-intermediate to advanced level, including candidates preparing for the Cambridge Certificate in Advanced English or Cambridge Proficiency examinations. Its organisation differs from that of most conventional dictionaries, although an index allows you to find the word you need quickly.
Words are organised into word banks that help learners develop their writing. You are given related words from the same semantic fields, together with plenty of examples showing how they are used in natural contexts. There is also extensive coverage of collocations. This makes the dictionary particularly valuable for learners who want to move beyond knowing individual words and learn how to combine them effectively.
4. Oxford Advanced Learner's Dictionary with DVD (2015)
Suitable for learners from upper-intermediate to advanced level. This edition contains 63,000 references, 65,000 definitions, 90,000 examples, 11,600 idioms and phrasal verbs, 1,700 illustrated words and 2,800 new words and meanings. It is based on the British National Corpus. It is one of the leading dictionaries published in the UK and meets the important criteria for a dictionary at this level.
5. Longman Dictionary of Contemporary English
With 230,000 words, phrases and meanings, this dictionary provides extensive information for advanced learners. Its expanded grammar information gives additional help with grammar patterns and the use of appropriate tenses. Definitions are presented in order of frequency and are supported by natural examples. The dictionary also provides extensive comparison of spoken and written English, including information about frequency.
6. Collins COBUILD Concise Learner's Dictionary
This dictionary has many of the features found in the high-level dictionaries listed above and is particularly suitable for learners who need English for academic purposes, for example those planning to study at a UK university.
The Collins COBUILD project revolutionised dictionary design in the early 1980s. Since then, the other major publishers have caught up, and there is now relatively little to choose between the leading advanced learners' dictionaries. The main differences tend to be differences of emphasis, which may appeal to learners with different learning styles and purposes.
Conclusion: For most serious learners of English, an English-English dictionary is a better long-term investment than a bilingual dictionary. If you develop the confidence to work with explanations in English, you will not only be able to use the dictionary more effectively but may also learn more from your encounters with English during a visit to the UK.