unitimaginarynumber
nounUK /ˈjuːnɪt ɪˈmædʒɪnəri ˈnʌmbə/
US /ˈjuːnɪt ɪˈmædʒɪnəri ˈnʌmbər/
A special number that, when you multiply it by itself, gives you minus one.
The unit imaginary number is usually written as i, and i times i equals -1.
OTHER MEANINGS
2. A generator of the imaginary part of the complex number system, satisfying i² = -1.
Every complex number can be written as a + bi, where i is the unit imaginary number.
3. The point (0, 1) on the complex plane, representing a 90-degree rotation.
Multiplying by the unit imaginary number rotates a complex number by a quarter turn.
4. A basis element used to extend the real numbers into the complex numbers.
Together with 1, the unit imaginary number forms a basis for the complex numbers over the reals.