# Imaginary Number

An imaginary number is a number whose square is less than or equal to zero. For example, is an imaginary number and its square is . An imaginary number can be written as a real number multiplied by the imaginary unit, which is defined by its property .

An imaginary number can be added to a real number to form a complex number of the form, where and are called, respectively, the real part and the imaginary part of the complex number. Imaginary numbers can therefore be thought of as complex numbers whose real part is zero. The name "imaginary number" was coined in the 17th century as a derogatory term, as such numbers were regarded by some as fictitious or useless, but today they have a variety of essential, concrete applications in science and engineering.

Read more about Imaginary Number:  History, Geometric Interpretation, Applications of Imaginary Numbers, Multiplication of Square Roots

### Famous quotes containing the words imaginary and/or number:

All legendary obstacles lay between
Us, the long imaginary plain,
The monstrous ruck of mountains
John Montague (b. 1929)

I who have been involved with all styles of painting can assure you that the only things that fluctuate are the waves of fashion which carry the snobs and speculators; the number of true connoisseurs remains more or less the same.
Pablo Picasso (1881–1973)