When to use the nominative:
Subjects are always in the nominative case. The subject of a sentence is the person or thing that is “verbing” (doing the verb). To find the subject, look for the verb and ask “Who or what is [verb]ing"?
Example: Who or what is [sing]ing? Who or what is [sleep]ing?
Sometimes the subject of a sentence is a word immediately followed by a form of 'sein' or 'werden'. This type of subject is called a predicate noun. To find this type of subject, look for the form of sein and ask "What is this/that" or "Who or what is being"?
Example: What is that? Who is (being) the teacher?
Example: Who or what is [sing]ing? Who or what is [sleep]ing?
- The bird is singing. A man is sleeping.
Sometimes the subject of a sentence is a word immediately followed by a form of 'sein' or 'werden'. This type of subject is called a predicate noun. To find this type of subject, look for the form of sein and ask "What is this/that" or "Who or what is being"?
Example: What is that? Who is (being) the teacher?
- Das ist ein Hundhaus. (The subject is being a doghouse) Der Lehrer ist Kap Elliott. (Kap is being the teacher)