“双向的”用英语怎么说？

把祈祷想成一种 双向 的交谈.Think of prayer as a two - way conversation.我不明白为什么这个原则不能是双向的?I don't understand why this doesn't flow both ways.阀座阀瓣应该是双向的,能够延长止回阀寿命.Seat discs shall be reversible to extend check valve life....