Adjektivdeklination: after definite article (der, die, das) – Telc B1

After der, die, das (and deren, etc.) the adjective usually takes -e in nominative singular (der gute Mann, die gute Frau, das gute Kind) and -en in accusative masculine and in all plural/dative/genitive. So: den guten Mann, die guten Kinder, mit dem guten Freund. Learning the table for "after definite article" covers a large part of everyday usage.