The world of craft beer is filled with obscure terminology. Brewers plaster labels with mysterious numbers and abbreviations like ABV, IBU and Degrees Plato. Bars and restaurants advertise firkins of specialty brews. How is the average beer drinker to make sense of all this?

At beer tasting events, I am often asked to explain these terms. So here it is: a short lexicon of commonly encountered beer terms for non-geeks.

ABV: Alcohol by Volume. This is the percentage of alcohol in beer when measured by volume. Average beers contain about 5 percent ABV. The current world's strongest beer, Start The Future, by Dutch Brewery Het 't Koelschip, has 60 percent ABV.

Ale and lager: These are broad categories of beer that each contain many styles. The primary difference between them is the type of yeast used for fermentation. Ale yeasts ferment at higher temperatures, which promote the production of natural byproducts imparting fruity or spicy flavors into beer.

Lager yeasts ferment at low temperatures that inhibit production of those byproducts, resulting in a clean, crisp flavor profile. Examples of ales include pale ale, stout and hefeweizen. Examples of lagers are pilsner, bock and Oktoberfest.

Bottle-conditioned: Many commercial beers are force-carbonated at packaging by injecting them with CO2 under pressure. Bottle-conditioned beers are naturally carbonated by refermentation in the bottle. By adding small amounts of yeast and sugar at bottling, brewers induce fermentation that produces CO2 and creates carbonation. Bottle-conditioned beers have a sediment of yeast that in most cases should be left in the bottle. For German wheat beers, though, you want to swirl that yeast before pouring.

Cask-conditioned: Many Twin Cities bars and restaurants have begun offering cask beers. Cask-conditioned beers are carbonated naturally in the keg in the same way that bottle-conditioned beers carbonate in the bottle. Cask beers have lower carbonation than keg beer, giving them a creamier mouth feel. They are often served at "cellar temperature," around 55 degrees.

Firkin: A keg type commonly used for cask-conditioned beers. When bars advertise a firkin of a particular beer, it means they have a cask-conditioned version of that beer.

Degrees Plato: One of the more esoteric things found on craft beer bottles, this scale measures the amount of sugar in unfermented beer. A higher number indicates more sugar. More sugar means more alcohol.

IBU: International Bittering Unit. This is a measurement of beer bitterness. Hops lovers should look for beers with a high IBU number as higher numbers indicate more bitter beers. Typical American lagers have 8 to 15 IBUs while double IPAs may have more than 100.

SRM: Standard Reference Method. This is a system for measuring beer color. Higher numbers indicate darker beers. Pilsners have an SRM of about 4, while the SRM for stouts is above 20.

Michael Agnew is a certified cicerone (beer-world version of sommelier) and owner of A Perfect Pint. He conducts private and corporate beer tasting events in the Twin Cities and can be reached at