it's a small world idiom saying
这世界真小；真有这等巧事；无巧不成书
said to show your surprise that people or events in different places are connected
You know my old science teacher! Well, it's a small world, isn't it? 原来你认识我以前的科学课老师！嘿，这真是太巧了，不是吗？
江苏热线英汉汉英双解词典包含207361条英汉翻译词条，涵盖了常用英语单词及词组短语的翻译及用法，是英语学习的必备工具。