Editor’s pop quiz: When do you use "lie" rather than "lay"? What about "capital" as opposed to "capitol"? Here’s a particularly worrisome pair: affluent and effluent.

Confusing Words is a handy online tool for sorting out these and 3,200 more words that are "troublesome to readers and writers." With simple definitions and illuminating examples of correct usage, it’s like a digital Strunk & White. (Or maybe you think that should that be, "…its like a digital Strunk & White." Check the site to be sure.)