reciproc- +

1. Something that is mutual or done in return; given or felt by each toward the other; mutual: "We had a reciprocal respect for each other."
2. Given, performed, felt, etc., in return; given or shown by each of two sides or people to the other.
3. Corresponding; matching; complementary; equivalent: "We were able to have reciprocal privileges at other health clubs."
4. In grammar, with reference to a pronoun or verb; expressing mutual relationship or action: “Each other” and “one another” are reciprocal pronouns.
5. Inversely related or proportional; opposite.
6. In mathematics, noting expressions, relations, etc., involving reciprocals; such as, a reciprocal function.
7. Either of a pair of numbers whose product is 1; for example, the number 3 is the reciprocal of ⅓, and ⅓ is the reciprocal of 3.
8. Etymology: from Latin reciprocus, "turning back the same way, alternating", which stands for reco-procos and is a compound of the adjectives recos, "turning backward", and procos, "turning forward"; therefore, reciprocus originally meant "turning backward and forward".

Reciprocal, when all things are considered, is a compound adjective based on the elements re-, "back, backward" and pro-, "for, forward".

Any altruistic behavior occurring between individuals who are not related, based on the principle that help offered in one instance will be returned when the need for help is reversed.

In genetics, a genetic cross of two genotypes in which sex influences the outcome; for example, the cross of a male horse with a female donkey results in a hinny, while the cross of a female horse with a male donkey results in a mule.

In psychiatry, a tenet of social learning theory, that behavior is a result of the interplay between cognitive and environmental factors.

People learn by observing others and imitating their actions (modeling), and negative behavior patterns can be suppressed or eliminated by having a person learn different ways of behaving from other people (role models).

Two hybrids, one descended from male of one species and the female of another species, the other from a female of the first and a male of the second; such as, the mule and the hinney (sterile offspring of a male horse [stallion] and a female donkey).

1. In physiology, a condition in which the action of one group of a pair of antagonistic muscles is inhibited by the excitation of the other group, as when the biceps is prevented from contracting and bending the arm at the elbow while the triceps is extending the arm; a result of reciprocal innervation.
2. In psychology, the inhibition of an anxiety-provoking response by the practice of deep muscle relaxation.
3. Behavior therapy in which the patient is exposed to anxiety-producing stimuli while in a controlled state of relaxation so that the anxiety response is gradually inhibited.

In psychiatry, a form of behavior therapy in which the patient, while made to relax in comfortable surroundings, is gradually exposed to increasing amounts of anxiety-provoking stimuli.

In this way the patient can tolerate these stimuli and may eventually learn to dissociate the anxiety from them.

In physiology, the innervation of muscles around the joints, where the motor centers are connected in pairs in such a way that when one is excited the motor center of the corresponding antagonist is inhibited.

A relation of mutual dependence or action or influence.

Interchanging; each giving or doing to the other the same thing.

1. In a reciprocal manner; so that each affects the other, and is equally affected by it; interchangeably; mutually.
2. In the manner of reciprocals.
3. In mathematics: reciprocally proportional; proportional, as two variable quantities, so that the one shall have a constant ratio to the reciprocal of the other.

The quality or condition of being reciprocal; mutual return; alternateness.

1. To give, feel, do, etc., in return.
2. To give and to receive mutually.
3. Etymologically, "to move backward" and "forward".

1. Interchanging; each person or group giving or doing to the other the same thing; to give, to feel, etc., in return.
2. To give and to receive reciprocally; to interchange; such as, to reciprocate favors.
3. To cause or to move alternately backward and forward.
4. To make a return, as for something given.
5. To move alternately backward and forward.

Another term for a piston engine; that is, an engine that employs one or more pistons to convert pressure into a rotating motion.