Mein Bruder ist ein Professor.

English Translation

My brother is a professor.

I thought we didn’t use articles with profession names. “Meine Frau ist Lehrerin”, “Mein Vater ist Arzt”, “Mein Bruder ist Professor”. Nicht wahr?


Good question. You can say both.
It is difficult to explain the small difference.
If you just want to indicate the profession, you do not use the article.
However, if you want to express that the profession is something noteworthy, you can use the article.
If you add an adjective, you must use the article:
“Mein Bruder ist ein bekannter Professor”
(My brother is a well-known professor).

Note that in Germany “Professor” is both a profession and an academic title, ranging well “above” the doctorate. Therefore a “Professor” is still a “Professor” in retirement.
The title is used - contrary to the “Doktor” - without the name, so it’s “Herr Doktor Schmidt” but “Herr Professor”. Almost every Professor is also a Doktor, (Prof. Dr.), but don’t adress a Professor as Doktor, that’s an insult. Outside business and academia the titles are generally not used anymore; only old people (and Austrians :wink:) still do.
Formerly a wife of a Professor was “Frau Professor”. That’s no longer the case, unless of course, she has her own title.