"The teacher is a man."

Translation: Magister est vir.

[Ex0.nomist]

When do we use magistrum and when magister

[Mare1111]

Magister is the nominative (subject) and magistrum is the accusative (object) so "magister videt discipulum" translates to "the teacher sees the student." "Discipulus videt magistrum" translates to "the student sees the teacher"

[JeremyPavl]

Why is it not "magistra"?

[JennyRusse1]

That would be feminine, but he’s a man.

[justCharlyvibing]

Why is magistrum incorrect. What would be a sentence I would use magistrum in?

[Moopish]

Magister is the nominative case and is used as the subject of the sentence, usually the person or thing doing the action. It is used here since magister and vir are the same person and est simply links the two words together.

Magistrum the accusative and is usually used when an action is being done to the teacher:

Discipulus magistrum videt -> 'The student sees the teacher.'

Discipuli magistrum habent -> 'The students have a teacher.'