in general, something that is mutual, or which is returned equally on both sides, or that affects both parties alike.

RECIPROCAL Terms, among logicians, are those which have the same signification; and consequently are convertible, or may be used for each other.

in Mathematics, is applied to quantities which multiplied together produce unity. Thus \( \frac{1}{x} \) and \( x \), \( y \) and \( \frac{1}{y} \), are reciprocal quantities. Likewise \( \frac{1}{x} \) is said to be the reciprocal of \( x \), which is again the reciprocal of \( \frac{1}{x} \).

RECIPROCAL Figures, in Geometry, those which have the antecedents and consequents of the same ratio in both figures.

RECIPROCAL Proportion, is when in four numbers the fourth is less than the second, by so much as the third is greater than the first, and vice versa. See PROPORTION and ARITHMETIC, chap. vi. Great use is made of this reciprocal proportion by Sir Isaac Newton and others, in demonstrating the laws of motion.