If you're not a native English speaker, I suggest you get one of these: LONGMAN ADVANCED AMERICAN DICTIONARY ( with CD-ROM ) -- American English LONGMAN DICTIONARY OF CONTEMPORARY ENGLISH ( with CD-ROM ) -- British English I have collections of dictionaries (more than 100), and I find the most accurate on what I want, for they also have useful notes on usage (social use of a word, difference between synonyms, culture and grammar notes). com (with audio pronunciation)
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.