Indefinite Articles in German

The indefinite article in German (ein, eine, ein) is used to refer to a non-specific or newly introduced noun that is not yet known to the listener. It corresponds to "a" or "an" in English. Like the definite article, the indefinite article must agree with the noun in gender, number, and case, but it lacks a plural form (in the plural, no article is used).

In the Nominative, the forms are ein (masculine), eine (feminine), and ein (neuter). Note that masculine and neuter share the same form in the Nominative. In the Accusative, only the masculine changes to einen, while feminine and neuter remain eine and ein. In the Dative, they decline to einem (masculine and neuter) and einer (feminine). In the Genitive, the forms are eines (masculine and neuter, with nouns taking -(e)s) and einer (feminine).

A major distinction in German is that the negative article kein declines exactly like the indefinite article ein, but it can be used in the plural (e.g., keine Kinder). A common learner mistake is using the indefinite article with professions or nationalities after the verbs sein or werden (e.g., saying Ich bin ein Arzt instead of the correct Ich bin Arzt). Another frequent error is using ein in the plural, which is grammatically incorrect.