This is the 9329th most frequent German word.
mathieu
"Mathieu" is not a German word; it is a French proper noun, typically a first name equivalent to "Matthew" in English.
Mathieu in this context is used as a proper noun, specifically the name of an individual, indicating who the subject of the sentence is.
Mathieu arbeitet als Ingenieur in Berlin.
Mathieu works as an engineer in Berlin.
Mathieu is used to signify possession or association, indicating who possesses the mathematical abilities in question.
Die mathematischen Fähigkeiten von Mathieu sind beeindruckend.
Mathieu's mathematical abilities are impressive.
Mathieu is referred to as the person with whom the speaker has had a conversation.