Meaning/Usage: Used when a person knows someone you know by chance 用于某人偶然認識你認識的人時
Explanation: The world is very large with a lot of people in it. When two people know the same person by chance, then the world doesn't seem so big. In this case, the phrase "what a small world" is commonly used.
"I didn't know that you knew my uncle. What a small world."
"You have family in Florida too? What a small world."
"I went to high school with his mom, what a small world."
A. "Do you see that guy over there?"
B. "Yes, what about him."
A. "We used to play football together in high school."
B. "Wow, what a small world!"
Other Common Sentences
"What are the chances of that?"