刘先生的英文是（Mr. Liu）。
例句：
1、刘先生决定请一家名为“中华家脉”（My China Roots）的小公司来帮他寻根。
He decided to hire a tiny startup called My China Roots based near Beijing's Confucius Temple.
2、“山寨”应用程序也损害了手机游戏APP开发者刘先生。
Fake apps also hurt the interests of a mobile game developer surnamed Liu.
3、生活在澳大利亚悉尼的刘先生想要探寻家族根源，他毫不费劲地用家中的电脑搜索到，祖母的家族来自爱尔兰和英格兰。
When Adam Liu decided to research his family roots, he had no problem tracing his grandmother's family back to Ireland and England from his home computer in Sydney, Australia.
4、感谢给予职位尊敬的刘先生，正如我们电话中谈到的，我很高兴接受PPT公司提供的销售经理一职。
Dear Mr. Liu, As we discussed on the phone, I am very pleased to accept the position of marketing manager with PPT Company.
5、张先生生病时，刘先生任组长。
Mr.Liu acted as group leader while Mr.Zhang was ill.
