Noun-Declension 

Special Case n-Declension
Singular Plural
Nominative der Mensch die Menschen
Accusative den Menschen die Menschen
Dative dem Menschen den Menschen
Genitive des Menschen der Menschen

• All nouns in the n-declension are masculine.
• They always have the ending -en, except in the nominative singular.
• These nouns never have an umlaut in the plural.

Part of the n-declension are: 

1. All masculine nouns ending on -e

a) Animals
Hase Affe Ochse Löwe Affe Bulle Rabe [...]
b) Denominations of people
Bote Kollege Experte Junge Kunde Neffe Zeuge [...]
c) All inhabitants of countries ending on -e (except der Deutsche/die Deutsche = adjective declension)
Brite Franzose Tscheche Chinese Türke Schotte Russe [...]
3. All masculine noun with the endings -and, -ant, -ent, -ist, -oge, -at
Doktorand Elefant Student Pianist Biologe Soldat [...]
4. Many denominations for people
Nachbar Rebell Prinz Graf Bauer Held Herr [...]
5. Others (many words of Greek derivation)
Fotograf Philosoph Katholik Architekt Satellit Monarch Seismograph [...]

Exceptions: 

• Genitive on -ns, -n elsewhere: Friede, Glaube, Name, Buchstabe, Gedanke 

• Herz: das Herz, das Herz, dem Herzen, des Herzens, (Pl.) die Herzen