Utilization - the percentage of the total alpha acids of hops that are isomerized into the finished beer. Utilization usually tops off at 30%. Generally, the higher the boil gravity (the more sugars or saccharides), the less room there is for isomerized alpha acids from the hops to be dissolved in the wort--hence, lower utilization. See Isomers, Calculating IBUs, and Tinseth Formula.
Vorlauf - first part of the lautering process, following the mash-out, consisting of recirculating the wort back through the grain to set the grain bed in the mash tun / lautering tun for filtering out grain husks and particles while sparging. The vorlauf helps clarify the wort and prevents grains from entering the boil kettle which may produce astringent tannins.
Wort - the malt-sugar solution that is boiled before fermentation. The wort before boiling is called "sweet wort," after boiling with hops it is called "bitter wort." See Malt and Saccharides.
Yeast - one-celled fungi that make fermentation possible by metabolizing wort sugars (saccharides) and other nutrients, and producing ethanol and carbon dioxide in the process. The technical name for common brewer’s yeast (used for fermenting ales) is Saccharomyces cerevisiae (Gr. saccharo – sugar, myces - fungus. L. cerevisiae – of beer). The yeast generally used with lager brewing is Saccharomyces pastorianus (named in honor of Louis Pasteur). It is a close relative of the Saccharomyces cerevisiae yeast used for ales. See Yeast Pitching Rate, Yeast Profiles, Bottom Fermentation, and Top Fermentation.
Zymurgy - the science of brewing and fermentation, from Gr. Zume “leaven,” following the word pattern of metallurgy.