noun
physical constant
A fundamental, unchanging quantity in physics, such as the speed of light or Planck's constant.
See also: 万有引力定数 (ばんゆういんりょくていすう) · プランク定数 (プランクていすう)
光速度は重要な物理定数の一つです。
The speed of light is one of the important physical constants.
The values of physical constants are precisely measured through experiments.