English-English dictionary The best one to start with, in my opinion, is the Cambridge Learner's Dictionary. It provides audio pronunciation, both British and American, includes inflected forms and usually has several example sentences. http://dictionary.cambridge.org/dictionary/learner-english/ If you can't find a word there, or need a comparison, I would next check Merriam Webster. It will have more of the less common definitions included and has some information on etymology. http://www.merriam-webster.com/ Speaking of etymology, this site is a lot of fun. It will be most useful for linguist and advanced students. However, sometimes it can help people learning to not just understand the word or phrase, but also where it comes from. http://www.etymonline.com/ It can be useful in answering questions like one word can have two completely different meanings, for example: Incense - noun - material burned to produce a pleasant smell, like in church Incense - verb - to make angry