principle of superposition

principle of superposition
    n 1: (geology) the principle that in a series of stratified
         sedimentary rocks the lowest stratum is the oldest [syn:
         {principle of superposition}, {superposition principle},
         {superposition}]
    2: the displacement of any point due to the superposition of
       wave systems is equal to the sum of the displacements of the
       individual waves at that point; "the principle of
       superposition is the basis of the wave theory of light" [syn:
       {principle of superposition}, {Huygens' principle of
       superposition}]