The contents of this section is assumed to be known in the subsequent sections; please read it carefully. The examples in this section are only illustrative; the rules governing the contained declension endings are explained later.
There are three genders (masculine, feminine, neuter) and two numbers (singular, plural) but they combine only into four classes (masculine singular, feminine singular, neuter singular, common plural). The formation of a noun plural may be dependent on the gender of the word, but all other words – articles, pronouns, adjectives – referring to a plural noun are not affected by its gender. The four classes are abbreviated m, f, n, and p in this article. (The term “noun class” instead of “grammatical gender and number” is normally used for African languages but is useful here as well.)
Gender is not sex: non-biological, hence sexless, objects can have words of any gender. However, when a word denotes exclusively persons or animals of only one sex, there is a good chance that males have words of masculine gender and that females have words of feminine gender, although even then there are exceptions. Other than in English, the gender of generic words overrides the sex of the person; we can thus have eine männliche Geisel or ein weibliches Mitglied. In the same sentence, the grammatically fitting pronoun is used; later, there is often a switch to the “biologically correct” one. Most generic words of masculine gender have a feminine counterpart for females; one would therefore not say ein weiblicher Lehrer but rather eine Lehrerin. Whether or not Lehrer beiderlei Geschlechts can or should be replaced by Lehrerinnen und Lehrer is a matter of political correctness, not of language, and thus not discussed here.
There are four cases (nominative, genitive, dative, accusative), mostly enumerated in this sequence but sometimes also with accusative second. The four cases are abbreviated N, G, D, and A in this article. The way cases are marked by articles or by word endings depends on the class:
Only in the m class, A case is different from N case. This rule is universally valid and overrides every rule below. Thus, in the sequel a phrase like “only N case” would mean “only N case and, for f, n, or p class, also A case” without further notice.
In the f class, not only N und A case coincide, but also G and D, with an exception for names. Moreover, for nouns, but not for articles and adjectives, all four cases look the same.
In the p class, N, A, and G coincide for nouns.
Hence, the four classes combine with the four cases in a way that not 16 combinations result but only 10 for nouns (m-N, m-G, m-D, m-A, f-NGDA, n-NA, n-G, n-D, p-NGA, p-D) and 12 for other parts of speech (with f-NA, f-GD, p-NA, p-G). That’s a fair saving over 2×3×4=24 but the odd distribution of similar and dissimilar forms seems to be more of a difficulty than a simplification.
Since Middle High German times, endings marking the gender and case of a word are used rather sparingly, and many of the ending look the same or very similar. This sparingness can be considered a feature of German declension: when there is already a word having a more or less unambiguous mark for the case, then other words may have no mark or a rather unspecific one. This principle is sometimes called “Monoflexion” because in the extreme case, there is only one inflected word in the phrase; in general, however, more than one word is inflected. Here are some examples:
Er geht mit gutem Beispiel voran.
Das Kapitel beginnt mit einem guten Beispiel.
In the first sentence, gutem is the only word that has a chance of showing the n-D property of gutes Beispiel in this sentence. It carries the ending -em which is specific for mn-D. However, in the second sentence, einem has already a specific ending, and for the adjective a rather unspecific -en is good enough.
Mit wievielen Schülern hast du dich getroffen? – Mit drei Schülern.
Mit wievielen Schülern hast du dich getroffen? – Mit dreien.
This is again the same pattern: the p-D form differs from the other cases by an additional -n ending, so such an ending on the numeral is spurious and thus omitted. This happens also for words where the p-D form is not different from the other p forms.
Wessen Buch ist das? – Es ist dein Buch.
Wessen Buch ist das? – Es ist das deine.
Wessen Buch ist das? – Es ist deines.
Here, it is not case information but gender information which can be attached to either the noun, or the article, or the possesive pronoun. As a result, the latter can get three different possible endings although gender and case is always the same, to wit n-N.
When a name consists of several words, not all of them get the -s ending in the genitive case – sometimes even none when the article carries already the case information: Walters, Herrn Walter Müllers, des Herrn Walter Müller.
Whereas the principle of “sparingness of marking” has some logic behind it, the examples show that the actual endings appear somewhat irregular. There is only little freedom which spurious endings to drop or to retain; in most cases there is only one possible distribution of case endings.