Wiktionary
n. (context complex analysis English) A number of the form ''ai'', where ''a'' is a real number and ''i'' the imaginary unit
WordNet
n. a number of the form a+bi where a and b are real numbers and i is the square root of -1 [syn: complex number, complex quantity]
Wikipedia
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An imaginary number is a complex number that can be written as a real number multiplied by the imaginary unit , which is defined by its property . The square of an imaginary number is . For example, is an imaginary number, and its square is . Zero is considered to be both real and imaginary.
Originally coined in the 17th century as a derogatory term and regarded as fictitious or useless, the concept gained wide acceptance following the work of Leonhard Euler and Carl Friedrich Gauss.
An imaginary number can be added to a real number to form a complex number of the form , where the real numbers and are called, respectively, the real part and the imaginary part of the complex number. Some authors use the term pure imaginary number to denote what is called here an imaginary number, and imaginary number to denote any complex number with non-zero imaginary part.
Usage examples of "imaginary number".
Like the imaginary number system: it's used in circuit design, but it certainly wasn't intended for that.
But think of Adam and Eve like an imaginary number, like the square root of minus one: you can never see any concrete proof that it exists, but if you include it in your equations, you can calculate all manner of things that couldn't be imagined without it.
He jaunted along the space-time goedesics to Elsewheres and Elsewhens, translating `i', the square root of minus one, from an imaginary number into reality by a magnificent act of imagination.