Definition of: reciprocal

(ri·sip′rə·kəl) adjective
1. Done or given by each of two to the other; mutual.
2. Mutually interchangeable.
3. Alternating; moving to and fro.
4. So related, as two concepts, that if the first determines the second, then the second determines the first.
5. Expressive of mutual relationship or action: used in connection with certain pronouns and verbs or their meaning.
6. Math. Of or pertaining to a fraction the numerator and denominator of which have been reversed.
—noun
1. That which is reciprocal.
2. Math. The quotient obtained by dividing unity by a number or expression, as is the reciprocal of x. In a fraction, this reverses the numerator and denominator, as is the reciprocal of . See synonyms under MUTUAL. [<L reciprocus]
—re·cip′ro·cal′i·ty (-kal′ə·tē), re·cip′ro·cal·ness noun
—re·cip′ro·cal·ly adverb