Reinheitsgebot. If you know what it means, then you probably know that Germany makes some of the best beers on the planet.
Despite the Oktoberfest beer festival, German beer sales are falling
Reinheitsgebot is the purity requirement for German breweries that orders them only to use water, hops, barley-malt and yeast.
It dates from 1516 and has given Germany a proud history of quality ale.
But despite that, the locals are drinking less and less beer.
GERMAN BEER GUIDE
Altbier: Dark, hoppy
Koelsch: Pale, light-bodied
Weizen: Wheat beer
Berliner Weisse: Pale, sour
A government report says German beer consumption is at a 15-year low.
Some 10.4bn litres were sold last year, down 2.7% on 2006.
The German Brewers' Association blamed a rainy summer and the lack of a major sporting event.
But it also acknowledges that tastes are changing.
"Our regular customers are getting older and don't drink as much any more, and generally, Germans prefer milder tastes today and are more health-conscious," spokesman Marc-Oliver Huhnholz said.
The government's latest figures confirm that trend. Sales of soft drinks and for beer mixed with fruit juice jumped 18.1% in 2007.
Germany has 1,300 breweries, including what is claimed to be the world's oldest, the Benedictine abbey Weihenstephan, which started brewing in 1040.