The nominative case marks the subject of the sentence — the person or thing doing the action. It's the "default" form you already learn nouns in, so you've been using it since lesson one.
| German | English |
|---|---|
| Der Mann arbeitet. | The man works. |
| Die Katze schläft. | The cat sleeps. |
| Das Kind spielt. | The child plays. |
In "Der Mann arbeitet," what case is "der Mann" in?