An irreversible reaction is a reaction that, under the given conditions, proceeds essentially in one direction only, with the reverse reaction negligible. It is usually written with a single arrow. It contrasts with a reversible reaction, which can proceed appreciably in both directions and reach equilibrium.

不可逆反应是在给定条件下基本只朝一个方向进行、逆反应可忽略的反应。它通常用单箭头表示。它与可逆反应相对,后者能在两个方向上都明显进行并达到平衡。