University and research

Der Doktorand belongs to a small group of masculine nouns that grammars call weak, and a thesis or a letter to a supervisor is exactly where the difference shows. A weak noun adds -en in every form except the nominative singular: den Doktoranden, dem Doktoranden, des Doktoranden — with no -s in the genitive. So it is Sie trifft sich mit ihrem Doktoranden, and the bare dem Doktorand, heard often enough in speech, counts as a mistake on paper. This list has two more of them: der Kommilitone and der Privatdozent. The group can be spotted in advance. Masculine nouns for people that end in -and, -ant or -ent decline this way, and so do almost all that end in -e. The feminine forms, die Doktorandin and die Kommilitonin, are entirely regular.