This is the 6085th most frequent Polish word.
amerykanin
"Amerykanin" means "American" (a male person from the United States).
The word 'Amerykanin' is used as a noun to refer to a person from the United States.
Amerykanin podróżuje po Europie.
An American is traveling through Europe.
Here, 'Amerykanin' takes the accusative form 'Amerykanina' to fit the grammatical setup of the sentence, as it is the direct object.
Spotkałem sympatycznego Amerykanina na konferencji.
I met a nice American at the conference.
In this sentence, 'Amerykanin' is in the instrumental form 'Amerykaninem,' used after the preposition 'z' indicating by or with whom the speaking occurred.