3岁的男童可以用英文说 "a 3-year-old boy" 或 "a boy who is 3 years old"。这种表达方法在英语中是常见的，可以用来描述一个人的年龄。
例如：
"He is a 3-year-old boy." (他是个3岁的男童。)
"The 3-year-old boy loves to play with toys." (这个3岁的男童喜欢玩玩具。)
"She is taking care of a 3-year-old boy." (她在照顾一个3岁的男童。)
希望这对您有帮助！
例如：
"He is a 3-year-old boy." (他是个3岁的男童。)
"The 3-year-old boy loves to play with toys." (这个3岁的男童喜欢玩玩具。)
"She is taking care of a 3-year-old boy." (她在照顾一个3岁的男童。)
希望这对您有帮助！