Ich habe keinen Hund.
English: I have no dog.
The Negationsartikel in German is a special article used to make nouns negative. It is similar to saying 'no' or 'not any' in front of a noun.
Use the Negationsartikel 'kein' to say that there is none of something or that you do not have something. It is used before nouns instead of 'ein' or no article, especially with things you cannot count or do not have.
Ich habe keinen Hund.
English: I have no dog.
Wir trinken keinen Kaffee.
English: We do not drink coffee.
Sie hat keine Schwester.
English: She has no sister.
Es gibt keine Äpfel.
English: There are no apples.