Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Everything you could ask for in a dictionary

The Oxford English Dictionary has always been the standard by which all other dictionaries have been judged. However, while the 20 volume set is quite thorough, to say the least, it isn't the sort of thing you'd want to keep on your desk at work. (Unless you're employed as an English professor.) This "Shorter" two volume set is an excellent and more compact version of the full dictionary. While it lacks many of the historical word usage references (try looking up "apprehend" in the 20 volume set and compare it to this one, and you'll see what I mean), it is more than adequate for almost anyone. The thumb index tabs are very useful, and the books are bound beautifully. Along with the Oxford Canadian Dictionary, Roget's Thesaurus, and Strunk and White's "Elements of Style", this dictionary is one of the core reference books I use on a daily basis. Certainly costlier than many dictionaries, but in this case you really do get what you pay for.