Plumbing and sanitary engineering

A drain works by gravity, so a German plumber checks das Gefälle before anything else: the fall of a pipe, given as a ratio or a percentage, mit ausreichendem Gefälle verlegt. The word is built on fallen, and in the trade it stays literal. Outside the trade it is one of the commonest words in German for inequality. Das Lohngefälle zwischen Ost und West is the pay gap, ein soziales Gefälle a social divide, das Nord-Süd-Gefälle the difference in wealth between two halves of a country or of the world. English uses « gap » or « divide » for these, words with no downhill in them; German keeps the slope, so the difference always runs from higher to lower. A newspaper reader meets the second sense daily and may never need the first, while on a building site the second never comes up. The plural, rarely needed, is unchanged: die Gefälle.