The German adverb nicht and adjective kein can be used to negate a sentence as well. Nicht is the English equivalent of “not”. Kein, on the other hand, can have differing nuances depending on the sentence: no, not any, not a, none, no one, nobody.
The rules for applying kein and nicht are actually quite simple. (really!) They are as follows:
When Nicht Is Used in a Sentence
The noun to be negated has a definite article.
Er liest das Buch. Er liest das Buch nicht. (He is not reading the book.)
The noun to be negated has a possessive pronoun.
Er liebt seine Freundin. Er liebt seine Freundin nicht. (He does not love his girlfriend.)
The verb is to be negated.
Ich will schlafen. Ich will nicht schlafen. (I don’t want to sleep.)
An adverb/adverbial phrase is to be negated.
Sie rennt schnell. Sie rennt nicht schnell. (She does not run fast.)
An adjective is used with the verb sein.
Das Kind ist geizig. Das Kind ist nicht geizig. (The child is greedy.)
When Kein Is Used in a Sentence
The noun to be negated has an indefinite article.
Ich will einen Apfel essen. Ich will keinen Apfel essen. (I don’t want to eat an apple.)
The noun has no article.
Ich habe Zeit dafür. Ich habe keine Zeit dafür. (I don’t have time for that.)
Please note that though ein has no plural, kein does and follows the standard case declension pattern.
The Position of Nicht
The position of nicht is not always so clear-cut. However, generally speaking, nicht will precede adjectives, adverbs and either precede or follow verbs depending on its type.
Nicht and Sondern, Kein and Sondern
When nicht and kein negate only a clause, then usually the second clause that follows will begin with the conjunction sondern.
Ich will nicht dieses Buch, sondern das andere.
To put particular emphasis on nicht, positioning it at the beginning of the sentence is acceptable:
Nicht Karl meinte ich, sondern Karin.