Semiotics

Semiotics took der Index from Latin, and German kept the Latin way of making it plural. English speakers know the pattern from « index » and « indices », but German spells it its own way: the x of the singular becomes z before the ending, so it is der Index, die Indizes. The same change runs through the other learned nouns in -ex and -ix: der Kodex, die Kodizes; die Matrix, die Matrizes. Beside the Latin form most of them also have a plainer German plural in -e, die Indexe, die Kodexe. The trap lies one word away. Die Indizien, with an i before the ending, is the plural of das Indiz, a clue or a piece of circumstantial evidence, and ein Indizienprozess is a trial built on such evidence. Smoke is ein Index of fire in a seminar and ein Indiz for fire in a courtroom, and the two plurals must not be mixed.