Ever wonder what separates a Stout from an Imperial Stout? Or what really is the difference between an English-style India Pale Ale and an American-style India Pale Ale? Or why isn't there an Indian-style India Pale Ale? Well, there's a handy guide that can help answer two of those three questions for you, and it's available for free on the world wide web. (The answer to the third question: Irony's sake.)

Back on February 14th, the Brewers Association released their annual Valentine's Day gift for beer lovers everywhere: the 2009 Beer Style Guidelines list. For those of you who prefer to be force-fed their hyperlinks, you can download the PDF file here.

I'm usually not big into guessing games, but how many different beer styles do you think the Brewers Association defines? Even avid beer enthusiasts might be surprised as the list continues to grow, but the casual drinker might want to add this one into their permanent trivia rotation: An easy way to impress your friends during your next happy hour. The answer after the jump... (I know, I feel guilty about forcing you to click through, too.)

Believe it or not, the Brewers Association classifies 138 different styles of beer! (I recounted them myself.) That doesn't mean they're all as distinct as separating, say, a Lager from a Porter. And, as they admit in the introduction, it's not an exact science. But it ain't all B.S. either. The bibliography references an impressive 56 resources. So go grab 138 of your favorite beers and see the differences for yourself!

Hmm... Actually, on second thought, I don't think I am legally allowed to recommend that. Beer style newbies are better off hitting up the Brewers Association's beer styles page for a more extensive crash course in 6 of the more popular styles. Whatever you drink after that is on you.

[via Musings Over a Pint]