It's clear in the case of compound nouns, double s should be used e.g. Bundesstraße, but with other words I cannot see a pattern.

To me it appears to be used somewhat randomly, e.g.:

das Maß
die Masse

I also remember daß that was deprecated in favour of dass. Is there an aesthetic or practical reason behind these spelling conventions?


6 Answers 6


Since the 1996 reform, the rule is very simple:


  • an ß when following a long vowel (Maß, Spaß)

  • ss when it follows a short vowel (Bass, Kasse, Essen)

But only after splitting the word into morphemes*:

Essen is made up of the morphemes "ess" and "en". Aßen is formed by first splitting up the word according to its morphemes and then applying any ß-rules. The new morphemes are "Aß" (long vowel) and "en". Consider a word like Ausschusssitzung, which when split along it's morphemes (aus-schuss-sitz-ung) doesn't leave any double-s to be replaced. In the first case we have "ess", and in the second case we have "aus".

Update and addendum: When writing in all uppercase ("Versalschrift"), such as on the cover of a book or on signage, the ß is replaced by SS (e.g. "DER GROSSE DUDEN"). In 2017, new rules were adopted that allow the use of a capital sharp s (ẞ, aka "versales eszett"). The character was rarely seen before, but can now be used in place of the capital double-s. Now, both "DER GROSSE DUDEN" and "DER GROẞE DUDEN" are permissible (of course, using a lowercase ß is still not permissible here). Usage of this new character is still quite rare, presumably because the character is not available on german keyboards and, if you manage to type it, the rendering can be a bit odd in some systems. Still, it's not every day we get a new character. :)

* Note that the morphemes aren't the same as the syllables:
  Consider words like zer-leg-en (or zer-le-gen). Morphemes are found by deconstructing the meaning of the word.

  • 3
    I think this might be different in Switzerland. Commented May 25, 2011 at 11:59
  • Yes, Switzerland has its own rules concerning the ß.
    – swegi
    Commented May 25, 2011 at 12:03
  • 25
    Switzerland's rule for ß is that there is no ß. :)
    – splattne
    Commented May 25, 2011 at 12:11
  • 2
    @Alenanno no, there was no reform to delete the ß in Germany. There was just a reform on how to use the ß. And the capitalization of nouns was introduced centuries ago and is valid in all conuntries.
    – splattne
    Commented May 25, 2011 at 18:39
  • 3
    @TheBlastOne: There has never been any serious suggestion to eliminate the ß and it has never been declared optional.
    – Wrzlprmft
    Commented Jul 26, 2014 at 18:04

Yes, there is a rule, which was introduced with the latest spelling reform.

If the vowel before is short/open, then you'll use ss.

  • Ass, Klasse, Schlüssel, Essen, Ross, Russland, Riss, vergessen, hässlich, dass

If the vowel before is long/closed, you'll use ß.

  • Füße, Ruß, Kloß, groß, genießen, Maßband, Schweiß

Diphthongs (ie/ei/au/eu) are usually considered long.

Beware, this rule doesn't help you to know if there's an ss/ß in at all. Many similar sounding words have only one s in them. That's just something you have to learn. (And it's very hard for German dyslexics, too!)

  • Looking at this: en.wikipedia.org/wiki/German_phonology I can see that there are short/closed vowels as well as dipthongs (example: außen). How does the rule handle those?
    – z7sg Ѫ
    Commented May 25, 2011 at 11:58
  • you're asking for the diphtongs? As I said, they are usually long. Can't think of an exception atm.
    – ladybug
    Commented May 25, 2011 at 12:00
  • it's ok, you extended your answer at the same time as I commented! I will try it out.
    – z7sg Ѫ
    Commented May 25, 2011 at 12:02
  • okay. :) just realized after you're question that my comment on umlauts was plain wrong, so thanks for asking anyway.
    – ladybug
    Commented May 25, 2011 at 12:03

This is tricky. A general rule is:

  • short vowel before the ess => ss (as in besser)
  • long vowel before an unvoiced ess => ß (as in Maß)
  • long vowel before a voiced ess => s (as in Vase)

I think there are still exceptions but these rules apply most of the time. The biggest problem for a foreigner might be to distinguish between voiced and unvoiced esses. I have no solution for that. As a native speaker only one of the two versions sounds right.

  • I don't know many German native speakers who actually make a difference between unvoiced and voiced s. I found this very hard to learn in foreign languages, actually. So I would consider the difference between single s and ss/ß rather irregular. There is no 100% rule for that, only for the ß or ss question.
    – ladybug
    Commented May 25, 2011 at 11:55
  • 2
    @ladybug: Yes, this is not easy. But in my opinion it's not irregular. For example ss is always pronounced unvoiced. If you force yourself to pronounce e.g. besser voiced, you'll notice how silly it sounds. Of course with s/ß the difference is more subtle but imho it's perfectly there.
    – musiKk
    Commented May 25, 2011 at 12:03
  • 1
    The general rule only distincts between ss and ß. As I said below: if there's a double s in at all, you usually just have to learn. If you know it, then you can use the rule to decide which double s (ss/ß) you'll have to use.
    – ladybug
    Commented May 25, 2011 at 12:47
  • 1
    @musiKk: You could improve your "rules" by saying that they don't apply to the final "ess" of a word. (As ladybug says, they can only distinguish ss/ß.) Examples with short vowel: Biss, bis, Kuss, Bus, das Fass, ...; with long vowel: Gras, Maß, Mus, Fuß, Kies, Grieß, ... Commented Jun 7, 2011 at 12:24
  • 2
    Actually, Erlebnis was written "Erlebniss" a bit more than a century ago ... books.google.com/ngrams/…
    – celtschk
    Commented Mar 3, 2014 at 22:47

It's easy for Switzerland: They have no ß.

In capitalized words, the ß is usually replaced by a double-S (but see edit and end of answer). There are very few fonts featuring a capital ß, and there's no direct way to type it. Most germans don't know it exists.

Please note that an ß is not simply two s after one another, it's a different character, which is why Bundes|straße can never have an ß at the end of Bundes.

Words never start with an ß.

An ß is always sharp, not vocalized (like the english s in ass, unlike the german s, which is very often pronounced like the z in lazy).

Whether or not you use an ß is usually determined by the length of the vowel preceding the s/ß: You never have an ß after a short vowel. For example, muß (must) used to be correct, but since '96, it's muss. Muße (leisure) has a long vowel, so it has an ß.

The ß is also usually found after a diphthong, as in beißen. Probably because diphthongs are usually also long.

EDIT: The capital ß (Versal-ß in German) is slowly gaining popularity since it has been adopted as an actual letter in Germany (without much fanfare). It had been part of the Unicode standard since 2008. Still, many fonts don't include it.

Here are some examples: Straße/STRAẞE/STRASSE Straße/STRAẞE/STRASSE.

Even though I really welcome it, it still looks strange to me.

  • An alternative way of rendering a capital “ß” is via “SZ”, especially in (but not restricted to) names, to avoid confusion with the “ss” version (“SCHIESSER” = “Schiesser” vs. “SCHIESZER” = “Schießer”). Commented May 25, 2011 at 12:26
  • 1
    Yes, but that's not the preferred way. I might do it in names to avoid ambiguity, but this would introduce the new ambiguity whether someone might actually ba named "Schieszer". It's just a bad idea to capitalize a name with an ß in, because the only way to do it unambigously looks SCHEIßE. For ordinary words, I would always choose ß->SS. Or just avoid capitalisation at all.
    – fzwo
    Commented May 25, 2011 at 12:33
  • @fzwo “that's not the preferred way” – depends on who you ask. It certainly is the preferred way for me (but then, I also spurn the neue Rechtschreibung) and until a few years ago it was found much more commonly than “SS”, although this trend has been reversing for decades. Commented May 25, 2011 at 12:42
  • @Konrad_Rudolph "until a few years ago it was found much more commonly than “SS”," WOW, HOW OLD ARE YOU?!? ;)
    – splattne
    Commented May 25, 2011 at 13:12
  • 1
    @Sean Patrick Floyd Yes, that is a special font, FF Cst Berlin, and it's still used on Berlin street signs. There are Fraktur-like versions of this ligature-ß as well, also found on Berlin street signs in old cities.
    – fzwo
    Commented May 25, 2011 at 14:32

While the rule set that is usually given (e.g., in Stefano Palazzo’s answer) is correct, it is historically grown and mainly aimed at native speakers to explain the difference between the reformed and the old spelling.

Language learners might prefer the following rules for the spelling of s sounds in German:

  • s and ß form a voiced–voiceless pair like b/p, d/t, or g/k with s representing the voiced s sound and ß representing the voiceless s sound.
  • The normal rules for doubling consonants after short vowels apply, however, ss is used instead of ßß, e.g., so instead of blaßß and haßßen (both with short a, voiceless s) we write blass and hassen.
  • The normal rules for terminal devoicing (Auslautverhärtung) apply, so an s after the vowel of a syllable may represent a voiceless s,
    • if the s is only voiceless due to terminal devoicing, e.g., in Gras (voiced in Gräser),
    • for making to identically sounding words distinguishable in written language (Unterscheidungsschreibung), e.g., in das (article, contrast with dass),
    • for no obvious reason, e.g., in beste.

As always, loanwords may deviate from these rules, e.g., we write sorry instead of ßorry and Sudoku instead of ẞudoku.


I may be able to help clarify some confusion - i am a German language teacher. The results of the 1996 spelling reform states that you should use the eszett "for the sharp (voiceless) [s] after a long vowel or diphthong one writes ß, as long as no other consonant follows in the word stem". The reforms of 1996 caused much debate and controversy - it was an attempt to simplify spelling and many native German speakers were not happy with the proposed changes. It is quite ascinating actually!!! Enough with the digression - btw a diphthong is a "sound formed by the combination of two vowels in a single syllable, in which the sound begins as one vowel and moves towards another (as in coin, loud, and side )". Hope this clarifies a few things.

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