\Re*cip"ro*cal\, a. [L. reciprocus; of unknown
origin.]
1. Recurring in vicissitude; alternate.
2. Done by each to the other; interchanging or interchanged;
   given and received; due from each to each; mutual; as,
   reciprocal love; reciprocal duties.
         Let our reciprocal vows be remembered. --Shak.
3. Mutually interchangeable.
         These two rules will render a definition reciprocal
         with the thing defined.               --I. Watts.
4. (Gram.) Reflexive; -- applied to pronouns and verbs, but
   sometimes limited to such pronouns as express mutual
   action.
5. (Math.) Used to denote different kinds of mutual relation;
   often with reference to the substitution of reciprocals
   for given quantities. See the Phrases below.
{Reciprocal equation} (Math.), one which remains unchanged in
   form when the reciprocal of the unknown quantity is
   substituted for that quantity.
{Reciprocal figures} (Geom.), two figures of the same kind
   (as triangles, parallelograms, prisms, etc.), so related
   that two sides of the one form the extremes of a
   proportion of which the means are the two corresponding
   sides of the other; in general, two figures so related
   that the first corresponds in some special way to the
   second, and the second corresponds in the same way to the
   first.
{Reciprocal proportion} (Math.), a proportion such that, of
   four terms taken in order, the first has to the second the
   same ratio which the fourth has to the third, or the first
   has to the second the same ratio which the reciprocal of
   the third has to the reciprocal of the fourth. Thus, 2:5:
   :20:8 form a reciprocal proportion, because 2:5:
   :1/20:1/8.
{Reciprocal quantities} (Math.), any two quantities which
   produce unity when multiplied together.
{Reciprocal ratio} (Math.), the ratio between the reciprocals
   of two quantities; as, the reciprocal ratio of 4 to 9 is
   that of 3/4 to 1/9.
{Reciprocal terms} (Logic), those terms which have the same
   signification, and, consequently, are convertible, and may
   be used for each other.
Syn: Mutual; alternate.
Usage: {Reciprocal}, {Mutual}. The distinctive idea of mutual
       is, that the parties unite by interchange in the same
       act; as, a mutual covenant; mutual affection, etc. The
       distinctive idea of reciprocal is, that one party acts
       by way of return or response to something previously
       done by the other party; as, a reciprocal kindness;
       reciprocal reproaches, etc. Love is reciprocal when
       the previous affection of one party has drawn forth
       the attachment of the other. To make it mutual in the
       strictest sense, the two parties should have fallen in
       love at the same time; but as the result is the same,
       the two words are here used interchangeably. The
       ebbing and flowing of the tide is a case where the
       action is reciprocal, but not mutual.

\Re*cip"ro*cal\, n.
1. That which is reciprocal to another thing.
         Corruption is a reciprocal to generation. --Bacon.
2. (Arith. & Alg.) The quotient arising from dividing unity
   by any quantity; thus 3/4 is the reciprocal of 4; 1/(a +
   b) is the reciprocal of a + b. The reciprocal of a
   fraction is the fraction inverted, or the denominator
   divided by the numerator.