Questions & Answers about Beiß nicht in den Apfel.
Because this is a command in German, specifically the informal singular imperative. When you give a command to one person you normally leave out du.
- du beißt = you bite
- Beiß! = Bite!
So Beiß nicht in den Apfel. is a command addressed to one person, and the du is simply understood.
Beiß is the imperative form of beißen for du.
A useful pattern is:
- infinitive: beißen
- du form: du beißt
- command to one person: beiß!
So German takes the du form and removes the ending -t. That gives beiß.
Compare:
- du kommst → komm!
- du liest → lies!
- du beißt → beiß!