阿贝数是德国物理学家恩斯特·阿贝发明的物理学数,也称"V-数",用来衡量介质的光线色散程度.

介质的阿贝数-- V_d 通用的的定义是:

其中n_d, n_F 和 n_C分别是物质在夫琅禾费光谱 d, F 和 C (氦黄线587.56纳米,氢兰线486.1纳米和氢红线656.3纳米)的折射率。n_F-n_C是主色散.

还有用汞绿线(546.07纳米)测定的折射率中n_e计算的阿贝数V_e :

光线色散程度越大阿贝数越小，反之光线色散程度越小阿贝数越大。光学玻璃的两个重要参数是折射率和阿贝数。肖特玻璃目录中光学玻璃的阿贝数界于20-90之间。

In optics and lens design, the Abbe number, also known as the V-number or constringence of a transparent material, is a measure of the material's dispersion (variation of refractive index versus wavelength), with high values of V indicating low dispersion. It is named after Ernst Abbe (1840–1905), the German physicist who defined it.