imaginary number

Meaning

Noun

• A number of the form bi, where b is any real number and i denotes the imaginary unit.
• A number of the form a + bi, where a and b are real numbers and b is nonzero.

Related

Similar words

• purely imaginary number

Narrower meaning words

• purely imaginary number

Broader meaning words

• complex number

Origin

• 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.