imaginary number

Definition

A number of the form bi, where b is any real number and i denotes the imaginary unit.

Etymology

The adjective imaginary in this context was first used (as French imaginaire) by René Descartes in 1673, La Geometrie, referring to imaginary numbers in the broad sense, as non-real roots of polynomials. Descartes' usage was derogatory, but the concept later gained acceptance through the work of Leonhard Euler and Carl Friedrich Gauss in the 18th century.

Example Sentences

• "If a#61;0, then x#61;ib is called an imaginary number. The message here is that we must introduce imaginary numbers in order to be able to solve quadratic equations in general."