Herr meaning and definition in german

Omitting Herr (or the female form Frau) when addressing a person with their last name is usually perceived as disrespectful, but it is more common when speaking about somebody who is not present, except in formal contexts. However, there may be contextual pitfalls and regional differences, which makes it advisable for learners not to leave out Herr (and Frau).
When people address each other with their last name, but say du to each other, the words Herr and Frau are always left out in most regions. In parts of western Germany, however, there is (or was) a system of saying du and Herr (Frau) among coworkers.