阻尼比是工程上的无因次量，描述系统在受到扰动后振荡及衰减的情形。许多系统在受扰动，离开其静平衡位置时都会振荡，例如吊在弹簧的重物，若用力往上拉再放开，就会上上下下的摆动。在摆动过程中，系统试图回到平衡位置，不过会出现过冲。有时系统会有损耗（例如摩擦力）会形成系统的阻尼，会使系统的振荡渐渐变小，最后衰减。阻尼比是描述系统的振荡多快可以衰减。

系统的振荡行为出现在许多不同的领域中，例如控制工程、机械工程、结构工程及电机工程等。振荡的物理量可能有很大的不同，振荡的可能是在大风中的建筑物，也可能是马达的速度，但利用范式、无因次化的分析可以描述这些现象**通的特性。

In engineering, the damping ratio is a dimensionless measure describing how oscillations in a system decay after a disturbance. Many systems exhibit oscillatory behavior when they are disturbed from their position of static equilibrium. A mass suspended from a spring, for example, might, if pulled and released, bounce up and down. On each bounce, the system is "trying" to return to its equilibrium position, but overshoots it. Sometimes losses (e.g. frictional) damp the system and can cause the oscillations to gradually decay in amplitude towards zero or attenuate. The damping ratio is a measure of describing how rapidly the oscillations decay from one bounce to the next.