Indefinite Article Declension (ein-words)

The indefinite article ein changes across the four cases just like the definite article does — but with two famous "gaps" where it shows no ending at all. The good news for learners is enormous: once you know the der/die/das table, you already know almost all of the ein table, because ein-words copy the der-word endings exactly — except in two cells. And the same pattern governs not just ein but kein (no) and every possessive (mein, dein, sein, ihr, unser, euer, Ihr). Learn this one pattern and you've learned the declension of more than a dozen of the most common words in German.

The complete ein table

(There is no plural column, because ein has no plural — see the indefinite article. For the plural you need kein, covered below.)

The two gaps: where ein differs from der

Put the endings of ein next to the endings of der and the relationship jumps out. The ending on each ein-form is the same ending as the matching der-word — -en, -em, -er, -es — with exactly two exceptions:

Read across each row. den → einen (both end in -en), dem → einem (both -em), des → eines (both -es), der → einer (both -er). The endings match the der-word every single time — except in three cells that are really two gaps:

1. Nominative masculine: der has -r, but ein has no ending.
2. Nominative and accusative neuter: das has -s, but ein has no ending (and neuter nominative = neuter accusative, so this is really one gap appearing in two rows).

Everywhere else, ein-words are der-words with "ein-" glued to the front. Memorizing the ein table is therefore not a second big effort — it's the der table you already know, minus two endings.

One noun, all four cases

Here is masculine ein Mann run through every case, so you can watch the article and noun change together. Masculine is the most instructive gender because all four forms are visible (the nominative gap, then -en, -em, -es):

Note eines Mannes: the article eines and the noun ending -es, with no apostrophe — German never uses an apostrophe for the genitive. Compare des Mannes with eines Mannes: identical noun ending, and identical -es on the determiner.

Same pattern: kein and all the possessives

This is where the table earns its keep. The ein-word endings apply, unchanged, to a whole family of words. kein (no, not any) and every possessive determiner decline with these exact endings — including the two gaps. The possessives are:

Because kein and the possessives do refer to plurals (you can have "no children" or "my children"), they take a plural set too — and the plural endings match the der-words exactly (die → keine, den → keinen, der → keiner). Only ein itself lacks the plural.

In keinen Bruder and meinen Vater you see the masculine accusative -en; in ihrem Chef the masculine dative -em; in unser Projekt the neuter accusative gap (no ending). Every one of these endings is borrowed straight from the ein table — which was itself borrowed from the der table. (For negation specifics, see kein; for possessives, see possessives.)

Common mistakes

Key takeaways

• The ein table is ein/eine/ein → einen/eine/ein → einem/einer/einem → eines/einer/eines.
• ein-words are identical to der-words except for two gaps: nominative masculine (ein, not einer) and nominative/accusative neuter (ein, not eines). Everywhere else the endings match der/dem/des/etc.
• The most common error is using ein where einen is needed in the masculine accusative: Ich habe einen Bruder, not ein Bruder.
• Genitive masculine/neuter is eines and the noun adds -(e)s with no apostrophe (eines Mannes).
• The same endings govern kein and all possessives (mein, dein, sein, ihr, unser, euer, Ihr) — so this one pattern unlocks more than a dozen high-frequency words. kein and the possessives also have plural forms; ein alone does not.