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]

The Collaborative International Dictionary of English v.0.48:

Energy \En"er*gy\, n.; pl. Energies. [F. ['e]nergie, LL.
   energia, fr. Gr.?, fr. ? active; ? in + ? work. See In, and
   Work.]
   1. Internal or inherent power; capacity of acting, operating,
      or producing an effect, whether exerted or not; as, men
      possessing energies may suffer them to lie inactive.
      [1913 Webster]

            The great energies of nature are known to us only by
            their effects.                        --Paley.
      [1913 Webster]

   2. Power efficiently and forcibly exerted; vigorous or
      effectual operation; as, the energy of a magistrate.
      [1913 Webster]

   3. Strength of expression; force of utterance; power to
      impress the mind and arouse the feelings; life; spirit; --
      said of speech, language, words, style; as, a style full
      of energy.
      [1913 Webster]

   4. (Physics) Capacity for performing work.
      [1913 Webster]

   Note: The kinetic energy of a body is the energy it has in
         virtue of being in motion. It is measured by one half
         of the product of the mass of each element of the body
         multiplied by the square of the velocity of the
         element, relative to some given body or point. The
         available kinetic energy of a material system
         unconnected with any other system is that energy which
         is due to the motions of the parts of the system
         relative to its center of mass. The potential energy of
         a body or system is that energy which is not kinetic;
         -- energy due to configuration. Kinetic energy is
         sometimes called actual energy. Kinetic energy is
         exemplified in the vis viva of moving bodies, in heat,
         electric currents, etc.; potential energy, in a bent
         spring, or a body suspended a given distance above the
         earth and acted on by gravity.
         [1913 Webster]

   Accumulation, Conservation, Correlation, & Degradation
   of energy, etc. (Physics) See under Accumulation,
      Conservation, Correlation, etc.

   Syn: Force; power; potency; vigor; strength; spirit;
        efficiency; resolution.
        [1913 Webster]

WordNet (r) 3.0 (2006):

correlation
    n 1: a reciprocal relation between two or more things [syn:
         correlation, correlativity]
    2: a statistic representing how closely two variables co-vary;
       it can vary from -1 (perfect negative correlation) through 0
       (no correlation) to +1 (perfect positive correlation); "what
       is the correlation between those two variables?" [syn:
       correlation coefficient, coefficient of correlation,
       correlation]
    3: a statistical relation between two or more variables such
       that systematic changes in the value of one variable are
       accompanied by systematic changes in the other [syn:
       correlation, correlational statistics]

Moby Thesaurus II by Grady Ward, 1.0:

35 Moby Thesaurus words for "correlation":
   allegory, analogy, balancing, comparative anatomy,
   comparative degree, comparative grammar, comparative judgment,
   comparative linguistics, comparative literature,
   comparative method, compare, comparing, comparison, confrontation,
   confrontment, contingency, contrast, contrastiveness, dependence,
   distinction, distinctiveness, interrelation, likening, matching,
   metaphor, opposing, opposition, parallelism, proportion, relation,
   relativity, simile, similitude, trope of comparison, weighing