relativity

relativity
    n 1: (physics) the theory that space and time are relative
         concepts rather than absolute concepts [syn: {relativity},
         {theory of relativity}, {relativity theory}, {Einstein's
         theory of relativity}]
    2: the quality of being relative and having significance only in
       relation to something else
    

relativity \rel`a*tiv"i*ty\ (-t?v"?-t?), n.
   1. The state of being relative; as, the relativity of a
      subject. --Coleridge.
      [1913 Webster]

   2. One of two theories (also called {theory of relativity})
      proposed by Albert Einstein, the {special theory of
      relativity}, or the {general theory of relativity}. The
      {special theory of relativity} or {special relativity} is
      based on the proposition that the speed of light is a
      constant no matter how observed, and is independent of the
      motion of the observer. From this follows several
      principles, such as the increase of mass with velocity
      (which has been confirmed: see {relativistic mass
      equation}) and the impossibility of acceleration to a
      speed greater than that of light; the equivalence of mass
      and energy, expressed by the famous equation E = mc^{2};
      and time dilation, which is the apparent slowing of a
      clock in a system, as observed by an observer in a system
      moving relative to the clock. The {general theory of
      relativity} is based on the proposition that there is no
      physical difference between gravitational force and the
      force produced by acceleration. From this follow several
      results, of which the bending of light rays in a
      gravitational field and the equivalence of the inertial
      and gravitational masses have been verified. The possible
      existence of {black holes} (believed by many astronomers
      to have been adequately proven) is another consequence of
      the theory.
      [PJC]
    

37 Moby Thesaurus words for "relativity":
      Einstein theory, balance, coequality, communion, community,
      contingency, continuum theory, corelation, correlation,
      correlativism, correlativity, correspondence, cosmic constant,
      dependence, equilibrium, equipollence, equivalence,
      four-dimensional geometry, four-dimensional space,
      fourth dimension, interrelation, inverse proportion, inverse ratio,
      inverse relationship, mutuality, other continuums,
      principle of equivalence, principle of relativity, proportionality,
      reciprocality, reciprocation, reciprocity, space-time,
      space-time continuum, symmetry, theory of relativity, time-space