1. Done, given, felt, or owed in return: a reciprocal invitation to lunch.
2. Existing, experienced, or done on both sides: reciprocal agreements between nations; reciprocal admiration between friends.
3. Grammar Expressing mutual action or relationship. Used of some verbs and compound pronouns.
4. Mathematics Of or relating to the reciprocal of a quantity.
5. Physiology Of or relating to a neuromuscular phenomenon in which the excitation of one group of muscles is accompanied by the inhibition of another.
6. Genetics Of or designating a pair of crosses in which the male or female parent in one cross is of the same genotype or phenotype as the complementary female or male parent in the other cross.
1. Something that is reciprocal to something else.
2. Mathematics A number related to another in such a way that when multiplied together their product is 1. For example, the reciprocal of 7 is 1/7 ; the reciprocal of 2/3 is 3/2 .
[From Latin reciprocus, alternating; see per1 in the Appendix of Indo-European roots.]
re·cip′ro·cali·ty (-kălĭ-tē), re·cipro·cal·ness (-kəl-nĭs) n.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2019 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.