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Deutschen
(noun) (masc.) (pl.)
Germans [weak/mixed declension]
In German, adjectives can be turned into nouns. (eg; der Alte = the old man) These nouns decline (have endings) just like adjectives do, depending on gender/quantity, case and the article used before it. Definite and indefinite articles (the, this, these) trigger "weak" and "mixed" endings respectively, which for plurals nouns always means an '-en' ending in every case.