German Spelling: When to Use s, ss or ß

If you first learned German before 1996, you may not be aware that the German spelling has undergone a number of reforms, changing the spellings of words you may be familiar with. For many German speakers, it was hard to let go of certain old spellings, but some German teachers may argue that the reforms have not gone far enough. For instance, it is still difficult for beginner students to sort out when to use s, ss, or ß in a German word.

Keep track of when to use s, ss, and the infamous ß using this handy guide, but beware of the exceptions!

Single –s

• At the beginning of words:
  der Saal (hall, room), die Süßigkeit (candy, sweet), das Spielzimmer (playroom)
• Mostly in nouns, adjectives, adverbs and a few verbs when preceded and followed by a vowel:
  lesen (to read), reisen (to travel), die Ameise (ant), gesäubert (cleaned)​
  Exception and Examples: die Tasse (cup), der Schlüssel (key); some common verbs -> essen (to eat), lassen (to let), pressen (to press), messen (to measure)
• After consonant -l, -m, -n, and -r, when followed by a vowel: die Linse (lentil), der Pilz (mushroom), rülpsen (to belch)
• Always before the letter –p: die Knospe (a bud), lispeln (to lisp), die Wespe (wasp), das Gespenst (ghost)
• Usually before the letter –t: der Ast (branch), der Mist (dung), kosten (to cost), meistens (mostly)​
  Exception Examples: Verb participles whose infinitive form have a sharp -s. See the rule about using –ss or –ß with infinitive verbs.

Double –ss

• Usually written only after a short vowel sound: der Fluss (river), der Kuss (der Kiss), das Schloss (castle), das Ross (steed)
  Exception Examples:
  bis, bist, was, der Bus
  Words ending in –ismus: der Realismus
  Words ending in –nis: das Geheimnis (secret)
  Words ending in –us: der Kaktus

Eszett or Scharfes S: –ß 

• Used after a long vowel or dipthong:
  der Fuß (foot), fließen (to flow), die Straße (street), beißen (to bite)
  Exception Examples: das Haus, der Reis (rice), aus.

Infinitive Verbs with –ss or –ß

• When these verbs are conjugated, then these verb forms will also be written with either –ss or –ß, though not necessarily with the same sharp –s sound in the infinitive form:
  reißen (to rip) -> er riss; lassen -> sie ließen; küssen -> sie küsste