English negates almost everything with not. German has two words, and choosing between them is mechanical once you know what the test is.
The test
Use kein if you are negating a noun that has ein, or no article at all. Use nicht for everything else.
Ich habe einen Hund. → Ich habe keinen Hund.
Ich habe Zeit. → Ich habe keine Zeit.
Ich kenne den Mann. → Ich kenne den Mann nicht.
That is the whole rule. kein replaces ein; where there was no article, kein goes in. If the noun already has der, die, das, mein, dieser and so on, ein was never there to replace, so you need nicht.
kein takes endings
kein declines exactly like ein, and in the plural like meine.
| masculine | feminine | neuter | plural | |
|---|---|---|---|---|
| nominative | kein | keine | kein | keine |
| accusative | keinen | keine | kein | keine |
| dative | keinem | keiner | keinem | keinen |
Ich sehe keinen Mann. — I do not see a man. (accusative masculine)
Ich habe mit keinem Kollegen gesprochen. — I did not speak to any colleague. (dative)
If the case endings are unfamiliar, the four German cases covers where they come from.
Where nicht goes
nicht is the harder half, because its position changes what it negates. Two rules cover most sentences.
To negate the whole sentence, nicht goes as late as possible — but before anything that has to stay at the end.
Ich arbeite heute nicht. — I am not working today.
To negate one particular thing, nicht goes directly in front of it.
Das habe nicht ich gesagt. — It was not me who said that.
Ich fahre nicht nach Berlin, sondern nach Hamburg. — I am not going to Berlin, but to Hamburg.
What nicht has to stand in front of
Certain things are pinned to the end of a German sentence, and nicht goes before them rather than after.
| Pinned to the end | Example |
|---|---|
| a separable prefix | Ich rufe dich nicht an. |
| an infinitive | Ich kann heute nicht kommen. |
| a past participle | Ich habe das nicht gesagt. |
| an adjective after sein | Das ist nicht gut. |
| a place phrase | Ich wohne nicht in Berlin. |
The pattern underneath is that German holds the meaning-carrying part of the verb until the end, and nicht comes just before it. German word order explains why that end position exists.
The words that are already negative
Some words carry the negation themselves, and adding nicht on top is wrong.
| Positive | Negative |
|---|---|
| etwas — something | nichts — nothing |
| jemand — somebody | niemand — nobody |
| immer — always | nie — never |
Ich habe nichts gesagt. — I said nothing. (not "nicht nichts")
Two more negative pairs are built with nicht itself: schon — already → noch nicht — not yet; noch — still → nicht mehr — no longer.
doch, the answer English does not have
If somebody asks a negative question, German has a dedicated word for contradicting it.
Du kommst nicht mit? — Doch! — You are not coming? — Yes I am!
Nein confirms the negative (Nein, ich komme nicht mit); ja is ambiguous, and only doch clearly contradicts. That is why German speakers reach for doch constantly, while English speakers have to say "no, actually I am".
What to actually memorise
The ein test, and that nicht sits before whatever is pinned at the end. Everything else is the case endings for kein, which you are already learning for ein.
Check your understanding
Choose your answer before opening the explanation.
Ich habe ___ Auto. (nicht / kein)
Show answer and explanation
Ich habe kein Auto.
Use kein to negate a noun that would otherwise have ein or no article. Compare the definite noun in Ich kaufe das Auto nicht. The endings of kein still follow gender, number and case.