German spelling: ss or ß? (eszett)

The orthographic reform of the German language in 1990 simplified the use of ß (the spicy s, or eszett), and introduced more logical rules for language learners.

Use ß when…

The sound /s/ is written ß when it follows a long vowel or diphthong:
  • weiß (white) ; Fuß (foot) ; fließen (to flow) ; schießen (to shoot) ; büßen (to pay)
    ß can never be at the beginning of a word.

Use ss when…

The sound /s/ ss is written after a short vowel:
  • dass (that) ; Fass (barrel) ; messen (to measure) ; Riss (tear)
    In Swiss German, the question does not arise- ß does not exist.