Uninflected adjectives and adverbs

In brief

In German, an adjective after a verb such as sein (to be) describes the subject without changing its form: Der Kaffee ist heiß. An adverb describes how someone does something and also stays unchanged: Sie spricht langsam. The same basic word can serve both purposes: Das Auto ist schnell; das Auto fährt schnell.

Form

Subject + sein + unchanged adjective; subject + verb + unchanged adverb (often the basic adjective form).

Usage

• Use an unchanged adjective after sein to describe a person or thing.
• Use an unchanged adverb to say how an action happens; German often uses the same word as for the adjective.

Examples

• Der Kaffee ist heiß. — The coffee is hot.
• Die Kinder sind müde. — The children are tired.
• Sie spricht langsam. — She speaks slowly.
• Er fährt schnell. — He drives fast.

Common mistake

❌ Der Kaffee ist heiße.

✅ Der Kaffee ist heiß.

After ist, heiß describes the coffee but takes no adjective ending.

Remember

After sein, the describing word keeps its basic form. To describe how an action happens, German often uses that same form without an English-style -ly ending.