Adjective usage

Adjectives are used to describe people and things. Their form does not change when they follow the noun or personal pronoun that they describe (nor when they are at the beginning of a sentence directly before the conjugated verb):

Nicos T-Shirt ist rot. (Or: Rot ist Nicos T-Shirt.)

An adjective can also come before the noun that it describes, in which case the adjective's ending changes according to the noun following it:

Nico trägt ein rotes T-Shirt.

This change in the adjective's form is known as adjective declension. There are three different declensions. Which of the three is used depends on the article before the noun: a definite article, indefinite article or no article.

Adjective declension after an indefinite article

The adjective is placed between the article and the noun:

In the nominative and the accusative cases, the adjective takes the ending of the definite article:

In the accusative case, the masculine article changes form, as does the adjective ending. The other forms stay the same.

Nico, du brauchst einen neuen Pullover, eine neue Hose, ein neues T-Shirt und neue Turnschuhe!

Exceptions:

Adjectives that end in -el or -er usually lose the e before the adjective ending:
dunkel: Nico trägt einen dunklen Pullover.
teuer: Der teure Pullover ist schön.

A few adjectives are not declined (super, extra and some adjectives describing color):
super: Das ist ein super Film.
extra: Möchtest du einen extra Teller für den Salat?