"That boy" can be expressed as "that boy" in Engpsh. It is a pronoun used to refer to a specific male individual, usually in proximity to the speaker.
Examples in Engpsh:
"Do you know that boy over there?"
"That boy is playing with a ball."
对应的中文翻译为：
"你知道那个男孩吗？"
"那个男孩在玩球。"