在这篇文章内，矢量与标量分别用粗体与斜体显示。例如，位置矢量通常用表示；而其大小则用来表示。检验变量或场变量的标记的后面没有单撇号「」；源变量的标记的后面有单撇号「」。

在电磁学里，推迟势指的是，响应含时电荷分布或含时电流分布，而产生的推迟纯量势或推迟矢量势。对于这进程，由于「前因」与「后果」之间必然的推迟关系，信号以光速从源位置传播到场位置，需要有限时间。在某源位置的电流或电荷分布，必须经过一段时间之后，才能够将其影响传播到场位置，产生对应的电磁作用。这一段时间的长久跟源位置与场位置之间距离的远近有关。

In electrodynamics, the retarded potentials are the electromagnetic potentials for the electromagnetic field generated by time-varying electric current or charge distributions in the past. The fields propagate at the speed of light c, so the delay of the fields connecting cause and effect at earlier and later times is an important factor: the signal takes a finite time to propagate from a point in the charge or current distribution (the point of cause) to another point in space (where the effect is measured), see figure below.