imaginary number

/IH0 M AE1 JH AH0 N EH0 R IY0 N AH1 M B ER0/
noun
  1. 1

    (strict sense) A number of the form bi, where b is any real number and i denotes the imaginary unit.

  2. 2

    (broad sense) A number of the form a + bi, where a and b are real numbers and b is nonzero.

Source: https://en.wiktionary.org/wiki/imaginary%20number