The indefinite articles: ein, eine
When we are not talking about a particular object or a particular person, the indefinite article is used.
Was ist das? – Das ist ein Stift.
It does not matter which pen it is, to whom it belongs, or whether it is blue, black, big or small. The sentence could refer to any pen. That is why the indefinite article ein is used, and not the definite article der.
| definite | indefinite | |
| masculine | der Stift | ein Stift |
| feminine | die Brille | eine Brille |
| neuter | das Buch | ein Buch |
In the plural, there are no indefinite articles. If an indefinite noun is used in the plural, there is no article in front of it.
| definite | indefinite | |
| plural | die Stifte | Stifte |
| plural | die Brillen | Brillen |
| plural | die Bücher | Bücher |