Here's why:
* Nationality vs. Adjective: "Polish" can be used as a nationality (referring to someone from Poland) or an adjective describing something related to Poland.
* Proper Use: You should use "Polish" as an adjective before a noun:
* Correct: He is a Polish citizen.
* Correct: He is a Polish man.
* Correct: He is of Polish descent.
Let me know if you have any more grammar questions!