Definition of imaginary number in US English:

imaginary number


  • A number that is expressed in terms of the square root of a negative number (usually the square root of −1, represented by i or j)

    ‘when imaginary numbers are squared, they yield a negative result’
    • ‘Historically, imaginary numbers first came to light when trying to solve cubic equations, rather than quadratics.’
    • ‘In the first Knuth describes an imaginary number system using the imaginary number 2i as its base, giving methods for the addition, subtraction and multiplication of the numbers.’
    • ‘Imaginary numbers (such as the square root of minus one) form a direct component of the wave amplitude, and thus the probability function, of a wave/particle.’
    • ‘Using a combination of real and imaginary numbers, known as complex numbers, turns out to be sufficient to solve virtually all mathematical problems!’
    • ‘Another very significant application of the imaginary number to the physical world comes from quantum theory.’