This is the 253rd most frequent Polish word.
mateusz
"Mateusz" is the Polish equivalent of the name "Matthew," meaning "gift of God."
In this sentence, 'Mateusz' is used as a proper noun identifying a person by their name.
Mateusz to mój przyjaciel.
Mateusz is my friend.
Here, 'Mateusza' is the genitive singular form of the proper noun 'Mateusz', indicating the person being referenced as the object of the verb.
Dzwonię do Mateusza, aby zapytać o projekt.
I am calling Mateusz to ask about the project.
In this sentence, 'Mateuszem' is the instrumental singular form of 'Mateusz', describing the person with whom the action is performed.