Ale - A fermented alcoholic beverage containing malt and hops, similar to but heavier than beer. Ales are brewed with "top-fermenting" yeasts at close to room temperatures, 50-70F (10-21C)

Beer - A fermented alcoholic beverage brewed from malt and flavored with hops.  
Middle English ber, from Old English bor, from West Germanic, probably from Latin bibere, to drink.

Black and Tan - Mixture of Stout and Ale or beer, usually specifically Guinness and Harp (since they are made by the same brewery. Often in the US with Guinness and Bass.  Also used to refer to Yuengling mixture of Porter and Beer.  See Half and Half.  Note: most Englanders call this Half and Half, not Black and Tan.

"Cut the dust" - A phrase used by Pennsylvania workers to describe the quenching effects of local beer at the end of a hard day in the fields and mines.

Half and Half - Mixture of bitter ale and Pilsner beer, hence Yuengling Porter and Beer.  Also used interchangeably with Black and Tan.  In England this is specifically Guiness and Harp.

kortz : 32 liquid ounces, always used when referring to quantities of beer. (colloquial) "Let's
get some Yuengling kortz and go upda A-hole." Also called jugs, bumpers, tankers.  From

Lager - A type of beer of German origin that contains a relatively small amount of hops and is aged from six weeks to six months to allow sedimentation. Also called lager beer. 
[German, short for Lagerbier : Lager, storehouse, cellar (from Middle High German leger, from Old High German legar, bed, lair.]  German - lag, liegen, verb; to lie, leave be. 

Porter - A dark beer resembling light stout, made from malt browned or charred by drying at a high temperature. Short for Porter's Ale because the porters of the London street markets were especially fond of it..  Note that Yuengling's is a beer and is cold lagered in the German style and as such is not a true porter,  IT'S BETTER!

Radler - German mixture or Beer and lemon soda (this is usually the good lemon soda, similar to Orangina if you are familiar with it..  Radler - (meaning "cyclist"; recently even some Germans call it "biker"). This name was apparently coined in the summer of 1922 when Franz Xaver Kugler, the owner of a mountain hut, found the cyclists were drinking him dry so diluted his beer with lemonade, claiming this to be a new drink he had invented specially to allow them to return home safely. See more on Weitzen beers.

Reinheitsgebot - This is the German (originally, Bavarian) purity law that restricts the ingredients that can be used to make beer to being water, barley malt, hops, and yeast. In the 1516 version of the law, only water, malt and hops were mentioned, because yeast was not isolated until the 19th century by Louis Pasteur. The Reinheitsgebot is actually part of a larger document called the "Biersteuergesetz" or "Beer Tax Law" which defined what beer was and how it should be taxed according to strength. 
"Rein" means clean or pure; "-heit" means "-ness"; so "Reinheit" means "cleanliness" or "purity".

In 1987, the Reinheitsgebot was repealed by the EC as part of the opening up of the European market. Many German breweries elected to uphold the Reinheitsgebot in their brewing anyway out of respect for their craft and heritage.
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The Schuylkill (river) -  Dutch for "hidden river"

Shandygaff - also Shandy - Half beer, half Ginger Ale or Ginger Beer.  Shandys can also be made with Lemonade or other soda.  Lemon soda and Beer is a Radler in German.

Yuengling - German Jüngling, "Young man". Pronunciation is the same. 

Ying Yang, Vitamin Y - colloquial for Yuengling Beer.

See also Beer FAQ