在宇宙学中，同移距离和普通距离是两种很相关的距离测量方式，用于定义两个天体之间的距离。

普通距离就是我们平常所使用的距离衡量方式，在宇宙时的某个特定时间用一系列的测量手段测量天体到地球之前的距离，由于宇宙膨胀，这个测量出来的距离会随着时间变化。而同移距离排除了宇宙膨胀的影响，给出了不随空间膨胀的距离结果。

同移距离和普通距离被定义成在当前时间相等，其他的所有时间普通距离随时间变化，而同移距离一直保持不变。

In standard cosmology, comoving distance and proper distance are two closely related distance measures used by cosmologists to define distances between objects. Proper distance roughly corresponds to where a distant object would be at a specific moment of cosmological time, which can change over time due to the expansion of the universe. Comoving distance factors out the expansion of the universe, giving a distance that does not change in time due to the expansion of space (though this may change due to other, local factors, such as the motion of a galaxy within a cluster). Comoving distance and proper distance are defined to be equal at the present time; therefore, the ratio of proper distance to comoving distance now is 1. At other times, the scale factor differs from 1. The Universe's expansion results in the proper distance changing, while the comoving distance is unchanged by this expansion because it is the proper distance divided by that scale factor.