他在家吃早餐用英语可以说：He has breakfast at home.
来源： 该短语是根据英语的基本语法构造而成的，在英语中，吃饭的动作用动词"to have"表示，因此可以说"to have breakfast"，而"at home"表示在家的地点。
例句：
"He has breakfast at home every morning." (他每天早上在家吃早餐)
"She usually has breakfast at home before going to work." (她通常在上班前在家吃早餐)
"I prefer to have breakfast at home because it's more relaxing." (我更喜欢在家吃早餐，因为更放松)