There are various heuristics as to when to use ~s or ~es with a noun in the genitive case.

However, if you look up most nouns in a dictionary you'll see ~(e)s, i.e. it seems largely a stylistic choice which ending you chose (with ~es often described as sounding somewhat antiquated or poetic).

For some specific nouns though the dictionary shows just ~s, and for some others it shows just ~es, i.e. only one form is correct.

E.g. according to the dictionary der Mund must be written as des Mundes, i.e. ~es, and der Geschmack must be written as des Geschmacks, i.e. ~s.

I'm interested in these cases where it's black and white, i.e. one of the other forms is mandatory, and it's not up to the writer to choose (as in the case of all those nouns marked as ~(e)s in the dictionary).

What rules govern the cases where a specific ending is mandatory?

This is a nice existing answer but for the ~es case it just explains the "easy" situations, i.e. those where just adding ~s would be weird, i.e. all nouns ending with s, ß, x or z, but not cases like Mundes.

Apologies if you feel this isn't sufficiently different from previous questions for it not to be marked a duplicate.

  • So, you are looking for the contrast between des Mundes vs des Abends?
    – Janka
    Commented Jul 22, 2018 at 16:59
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    To me only Mundes, Bundes, Kindes, Windes, Landes, Randes really seem right, omitting e sounds wrong; but I wouldn’t be surprised, if there were people here making contrary claims... We might investigate a tendency in nouns ending in and, ind, und! I suspect similarity to unz, anz, inz discouraged those forms.
    – Ludi
    Commented Jul 22, 2018 at 20:42
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    I claim, without proof, that the -es is mandatory if and only if the masculine or neutral noun ends on "d"...
    – RoyPJ
    Commented Jul 23, 2018 at 7:49
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    @RoyPJ Not quite. Abends was already mentioned. But it might be a rare exception and your assumption might point to the right direction.
    – Ludi
    Commented Jul 23, 2018 at 8:55
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    I am surprised they completely exclude des Geschmackes it is not common, but the frequency remains definitely measurable: books.google.com/ngrams/…
    – Ludi
    Commented Jul 23, 2018 at 18:42

1 Answer 1


From https://www.duden.de/sprachwissen/sprachratgeber/Genitiv-auf-s-oder-es:

Häufig entsteht bei der Genitivbildung ein- und zweisilbiger Substantive im Maskulinum und Neutrum Unsicherheit.

Substantive, die auf einen Zischlaut, beispielsweise -ss, -z oder -tz enden, bilden den Genitiv grundsätzlich auf -es, also des Hasses, des Glanzes, des Satzes, des Reflexes. Nur -s wird verwendet bei Substantiven, die auf -en, -em, -el, -er oder auch mit einer Verkleinerungssilbe enden, also etwa des Schwimmens, des Pegels, des Fahrers, des Büchleins, des Gärtchens.

Bei zahlreichen anderen ein- und zweisilbigen Substantiven im Maskulinum und Neutrum sind grundsätzlich beide Formen möglich, häufig spielt der Satzrhythmus eine Rolle. Der vollen Genitivform wird vor allem dann der Vorzug gegeben, wenn der Genitiv vorangestellt wird: des Tages Hitze, des Waldes Kühle. Auch bei Zusammensetzungen mit Fugen-s wird aus Klanggründen oft die -es-Form favorisiert: des Jubiläumsjahres, des Geschäftsfreundes. Bei zweisilbigen Substantiven mit unbetonter Endsilbe findet dagegen eher die kurze Form Anwendung, ebenso bei Substantiven, die auf Vokal oder Vokal + h enden: des Abdrucks, des Mitleids, des Schnees, des Flohs. Im Rechtschreibduden findet sich das optionale Genitiv-e übrigens unmittelbar hinter dem Artikel in eckigen Klammern, also z. B. Blut, das; -[e]s.


Genitive formation of one- and two-syllable nouns often leads to uncertainty in the masculine and the neutral.

Nouns ending in a sibilance, for example -ss, -z or -tz, always form the genitive on -es, i.e. of des Hasses, des Glanzes, des Satzes, des Reflexes. Only -s is used for nouns ending in -en, -em, -el, -er or even with a reduction syllable, such as des Schwimmens, des Pegels, des Fahrers, des Büchleins, des Gärtchens.

With numerous other one- and two-syllable nouns in the masculine and neuter, both forms are possible, often the sentence rhythm plays a role. The full genitive form is preferred especially when preceded by the genitive: des Tages Hitze, des Waldes Kühle. For sound reasons, the -es form is also often favoured for compositions with fugues: des Jubiläumjahres, des Geschäftsfreundes. For two-syllable nouns with unstressed final syllables, on the other hand, the short form is used, as well as for nouns ending in vowel or vowel + h: des Abdrucks, des Mitleids, des Schnees, des Flohs. In the spelling dictionary [Duden], the optional genitive-e is located directly behind the article in square brackets, e.g. Blut, das; -[e]s.

E.g. according to the dictionary der Mund must be written as des Mundes, i.e. ~es, and der Geschmack must be written as des Geschmacks, i.e. ~s.

According to Duden, both Mund and Geschmack can have both endings.

  • 1
    Thanks for the answer :) I've come across very similar summaries already - but I'd noticed other patterns that don't seem to be covered in the commonly stated rules. E.g. for Mund and a few other words ending in nd it seems mandatory (according to Langenscheidt) to write them with ~es, i.e. Mundes. So I was just wondering if there was a more expansive set of rules for the cases where both forms, i.e. ~s and ~es, are not valid. Commented Jul 23, 2018 at 18:37
  • @GeorgeHawkins According to Duden and Langenscheidt both endings are valid for Mund.
    – Scriptim
    Commented Jul 23, 2018 at 18:51
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    Yes - I've looked at other sources now and see they're not all consistent. Even Langenscheidt disagree with themselves. I have Langenscheidt Basic German and there it definitely says Mundes - maybe here they've decided Munds is so rare they're going to claim that Mundes is the only form, but in their more heavyweight dictionaries they also acknowledge ~s? This seems odd though, scanning through I see ~(e)s for nearly all m/n nouns, so they don't seem to make such a choice lightly (except in those cases where ~s on its own would be just weird, e.g. nouns already ending in an 's' sound). Commented Jul 25, 2018 at 12:14
  • @GeorgeHawkins I suspect that this differs at Langenscheidt in different old editions of the printed dictionaries. It should always be up to date online. Nonetheless, I would always follow the Duden for such questions, as it is decisive for official spelling in Germany.
    – Scriptim
    Commented Jul 25, 2018 at 17:13

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