When I first started teaching English back in the days before the internet and smartphones, students would come to class with their pocket dictionaries, and use them to look up the words they didn’t know. Many of them would also have a bigger dictionary at home. Of course, all that is a thing of the past since you can now have access to a multitude of online dictionaries on your smartphone for free, and in many cases hear how the words are pronounced.
The best way to test a dictionary is to actually use it, so here are links to some of the most popular online dictionaries, with notes on their particular features. I’ve divided the list into four categories: Learner’s, General, Bilingual, and Picture Dictionaries.
Cambridge Learner’s Dictionary — Create and share your own word lists and quizzes for free. Ideal for intermediate learners of English (CEF levels A2–B2). Also has a Business English section. UK and US audio pronunciation.
Longman Dictionary of Contemporary English Online — Now with the Longman English–Japanese Dictionary. UK and US audio pronunciation.
Macmillan Online Dictionary — My favourite online dictionary. Comes with a ton of great features including Games, Quizzes, and Puzzles. British English audio pronunciation.
Merriam-Webster Learner’s Dictionary — Set up an account to save words to your own vocabulary list. Also features Word of the Day and Quizzes.
Oxford Learner’s Dictionary — Search in English or American English. Also has a Grammar and Usage section. British and American audio pronunciation.
Reverso Dictionary — Features definitions written in language that is easy to understand, examples taken from actual texts and conversations, and explanations of grammar.
Collins Dictionary — More than 722,000 words, meanings and phrases. Comes with a Thesaurus.
Dictionary.com — Features include Word of the Day, Slideshows and Quizzes.
Dictionary of Slang — English slang and colloquialisms used in the United Kingdom.
Oxford Living Dictionaries — Free access to the largest current English dictionaries and thesaurus as well as helpful tips on grammar, usage, spelling, and more.
The Free Dictionary — Allows you to create your own personal homepage.
Wiktionary — Collaborative project featuring over 5 million entries.
Bab.la — With 44 online dictionaries, conjugation tables and multilingual phrases, the bab.la language portal will help you translate, learn and practice new languages.
Collins Online Dictionary — French, German, Spanish, Italian, Portuguese, Chinese and Hindi.
Larousse — The best free online French-English dictionary.
WordReference — Free online bilingual dictionaries for English to many other languages.
ESOL Help Online Picture Dictionary — 24 categories including Animals, Clothing and Food.
Merriam Webster Visual Dictionary Online — Explore the 15 major themes to access more than 6,000 images. For more advanced learners.
Pictures Wordlist — Pictures from the Oxford Advanced Learner's Dictionary.