彼此互相用英文怎么说

"彼此互相"用英语可以说成 "mutually" 或 "reciprocally"。

"mutually" 来源于拉丁语 "mutuus"，意思是"相互的"。

例句：

They have a mutually beneficial relationship. (他们有一种互利的关系。)
We agreed to help each other mutually. (我们同意互相帮助。)

"reciprocally" 来源于拉丁语 "reciprocus"，意思是 "互相地"。

例句：

They reciprocally exchanged gifts. (他们互相交换礼物。)
They have a reciprocal agreement. (他们有一项相互协议。)