Now from a quadric equation we derive, in like manner, the notion of a complex or imaginary number such as is spoken of above.
|imaginary number |
A type of complex number in which the multiple of i (the square root of -1) is not equal to zero. Examples of imaginary numbers include 4i and 2 - 3i, but not 3 + 0i (which is just 3). See more at complex number.