In English, “Chu先生” is typically translated as “Mr. Chu.” The term “先生” is a common honorific used in the Chinese language to address a man, similar to “Mr.” or “Sir” in English. Therefore, when addressing a Chinese man formally, you would use “先生” followed by his surname, which in this case is “Chu.”
For example, if you were to greet him in English, you might say, “Good morning, Mr. Chu.”