noun
: the part of a ray divided in two by double refraction that follows the ordinary laws of refraction because its speed is the same in all directions through the doubly refracting medium
noun
: the part of a ray divided in two by double refraction that follows the ordinary laws of refraction because its speed is the same in all directions through the doubly refracting medium
Webster's New International English Dictionary. Новый международный словарь английского языка Webster. 2012