The Collaborative International Dictionary of English v.0.48:

Correlation \Cor`re*la"tion\ (-l?"sh?n), n. [LL. correlatio; L.
   cor- + relatio: cf. F. corr['e]lation. Cf. Correlation.]
   Reciprocal relation; corresponding similarity or parallelism
   of relation or law; capacity of being converted into, or of
   giving place to, one another, under certain conditions; as,
   the correlation of forces, or of zymotic diseases.
   [1913 Webster]

   Correlation of energy, the relation to one another of
      different forms of energy; -- usually having some
      reference to the principle of conservation of energy. See
      Conservation of energy, under Conservation.

   Correlation of forces, the relation between the forces
      which matter, endowed with various forms of energy, may
      exert.
      [1913 Webster]