This article is from the rec.food.drink.beer FAQ, by John Lock with numerous contributions by others.
Belgian ales often carry additional wording on their labels
indicating their strength. This applies to their original malt
strength not their alcoholic strength. Variations may appear as
follows:
Single:
Dutch/Flemish - enkel (pron. 'ankle')
French/Walloon - ?
Double:
Dutch/Flemish - dubbel (pron. 'double')
French/Walloon - double (pron. 'doobluh')
Triple:
Dutch/Flemish - tripel (pron. 'treepel' or 'trippel')
French/Walloon - triple (pron. 'treepluh')
Quadruple:
Dutch/Flemish - quadrupel (pron. 'quadruple')
French/Walloon - quadruple (pron. 'quadrupluh')
Also on the Trappist Ale "La Trappe" you will see the Latin versions:
Angulus, Duplus, Triplus, and Quadruplus.
 
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