This book is the Greek translation of "Der, Die, Das: The Secrets of German Grammar" (ISBN 978-3-9524810-0-4), which was originally published in English. The challenge that foreign students of German face if they want to speak German well, is to accurately map German nouns to one of three grammatical genders: masculine, feminine or neuter. Native German speakers acquire their knowledge of the grammatical gender of German nouns from early on. They are not given formal instruction at school about matching nouns to their correct gender, and the topic is not covered in standard German grammar books. For the same reason, native speakers who give German language lessons to foreigners do not teach their students how to match nouns to their gender: One cannot teach what one has not been taught. This book fills that gap in that it explains the principles that map German nouns to a specific gender. This allows foreign students of German to unlock the gender of entire categories of nouns, thereby enabling students to speak German more confidently.