German has four grammatical cases: nominative, accusative, dative, and genitive. Each case can be thought of as container for a basic part of speech, although it is not limited to the following:
•Nominative = subject
•Accusative = direct object
•Dative = indirect object
•Genitive = possessives
The nominative case has multiple components but only one function: it contains the subject noun or pronoun. There are different ways a sentence can include a nominative subject. A predicate noun renames the subject (it can be substituted for the subject and refer to the same person, thing, etc.). A predicate adjective is simply an adjective that describes the subject.
Jochen ist mein Freund. (Jochen is my friend.)
This is an example of a predicate noun. Jochen is in the nominative, as is "mein Freund" (my friend).
Jochen ist freundlich. (Jochen is friendly).
This is an example of an adjective "freundlich" (friendly) that describes the subject, Jochen.
Genders of nouns
All German nouns have a grammatical gender. A noun can be masculine, feminine or neutral. Nouns typically come with an article (definite, indefinite, possessive, negative.) Below are the articles for masculine, feminine and neutral nouns in the Nominative case.
To form a "This/That/These/Those is/are", we always use "Das", regardless of the gender of the noun that follows, or whether it is singular or plural.
Das ist eine Blume. (This is a flower.) "die Blume" is a feminine noun.
Das sind die Kinder. (These are the children) "die Kinder" is a plural noun, hence "die".
Das ist kein Kaffee. (This is no coffee.) "der Kaffee" is a masculine noun.