What do you call two numbers whose product is one?

A number when multiplied by its multiplicative inverse, or its reciprocal, yields a product of one, which is known as the multiplicative identity of a number. All numbers have an inverse with the exception of zero, which cannot be multiplied by any real number to yield a product of one.

The inverse of a number corresponds to the type of number it is reciprocating; all real numbers yield real reciprocals, rational numbers yield rational reciprocals and complex numbers yield complex reciprocals. In linear algebra, when matrix A is multiplied by matrix B to produce the identity matrix, A is said to be nonsingular or invertible with its inverse being B.