This is the 9334th most frequent German word.
matthew
The German word "Matthew" does not exist; "Matthäus" is the equivalent of "Matthew" in English, typically a name.
In this sentence, 'Matthew' is used as a proper noun, serving as the subject of the sentence.
Matthew ist ein guter Freund von mir.
Matthew is a good friend of mine.
Here, 'Matthew' functions as a proper noun, used as the object of the sentence expressing the person being looked for.
Hast du schon Matthew gesehen?
Have you seen Matthew yet?
In this sentence, 'Matthew' is again a proper noun, acting as the subject in the dependent clause.