This is the 847th most frequent Chinese word.
吴
The Chinese word "吴" refers to a surname, the ancient Wu state, or Wu culture/language.
Here, '吴' is a surname used to identify the teacher referred to in the sentence.
这是吴老师的办公室。
This is Teacher Wu's office.
In this sentence, '吴' is part of a proper noun indicating the name of a location.
吴川是一个美丽的地方。
Wu Chuan is a beautiful place.
'吴' here indicates the name of an ancient state or kingdom, depicting historical context.