Weak declension or inflection of German adjectives
https://www.usinggrammar.com/german-grammar/adjectives-weak-declension…How do adjectives follow the weak declension? If adjectives occur together with one of the determiners ‘ der, dieser, jeder, mancher, welcher, derselbe, jener ’ or ‘ alle, sämtliche, beide, keine ’ before a noun, they follow the weak declension in the singular.Compare the forms in the tables below: Information: Choosing the correct case is required for the weak inflection.