Search Result for "principle of relativity":
Wordnet 3.0

NOUN (1)

1. (physics) a universal law that states that the laws of mechanics are not affected by a uniform rectilinear motion of the system of coordinates to which they are referred; 



WordNet (r) 3.0 (2006):

principle of relativity
    n 1: (physics) a universal law that states that the laws of
         mechanics are not affected by a uniform rectilinear motion
         of the system of coordinates to which they are referred