mandagen is the masculine singular definite of mandag.

mandagN

Kven

maanantaiN

Norwegian Bokmål – Kvendict-nob-fkv/src/N_nobfkv.xml:46779Edit on GitHub Suggest

vuossárgaN; mánnodatN

Norsk-nordsamisk ordbokdict-nob-sme/src/N_nobsme.xml:29037Edit on GitHub Suggest

Case	Sg	Pl
Indef	mandag	mandager
Def	mandagen	mandagene