1

This question already has an answer here:

I study German. I don't know when to write dein or deine. For example: Dein Buch and Deine Sporttasche.

marked as duplicate by Jan, Gerhard, Em1, Tom Au, tofro Sep 23 '16 at 7:47

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  • Hi and welcome to German Language Stack Exchange. Feel free to take a tour of the site. Visit the help center to learn more about how it works. Your question boils down to ‘how do I recognise a noun’s gender?’ – Jan Sep 22 '16 at 20:52
5

Dein is a Possesivartikel. It depends on what you are talking about.

For the case Nominativ (what you're talking about) there are the following rules:

  • Maskulinum (der) -> dein
  • Femininum (die) -> deine
  • Neutrum (das) -> dein
  • Plural (die) -> deine

So regarding your examples:

Das Buch (Neutrum) -> Dein Buch

Die Sporttasche (Femininum) -> Deine Sporttasche