在数学中，环R的特征被定义为最小的正整数n使得

这里的na被定义为

如果不存在这样的n，R的特征被定义为0。R的特征经常指示为char(R)。

环R的特征可以等价的定义为唯一的自然数n使得nZ是映射1到1_R的从Z到R的唯一的环同态的核。另一个等价的定义：R的特征是唯一的自然数n使得R包含同构于商环Z/nZ的子环。

In mathematics, the characteristic of a ring R, often denoted char(R), is defined to be the smallest number of times one must use the ring's multiplicative identity element (1) in a sum to get the additive identity element (0); the ring is said to have characteristic zero if this sum never reaches the additive identity.