"Polish" is the correct English translation for "波兰人".
In English, the nationality or origin of a person from Poland is referred to as "Polish." It is capitalized, as is the case with nationalities in English. The term "Polish" can be used as both a noun and an adjective, depending on the context. For example, you could say "He is a Polish man" or "She comes from a Polish background." The word "Polish" is derived from the name of the country, Poland, and is widely understood and used in English-speaking countries.
It's worth noting that "Polish" should not be confused with the verb form of the word, which refers to the act of making something shiny or smooth. For example, you would say "I need to polish my shoes" or "She spent hours polishing the silverware."
In conclusion, when referring to people from Poland in English, the correct term to use is "Polish," and it is essential to capitalize it as it is a nationality.