Is -4 a imaginary number

Answer 1

No, both positive and negative numbers are part of the so-called "real" numbers. The so-called "imaginary" numbers are outside the number line.

Imagine the real numbers as a line from left to right, and the imaginary numbers a a separate line, from top to bottom. The place where they meet is zero. Positive is to the right of zero, negative to the left, imaginary numbers like +i or +3i to the top of zero, and negative imaginary numbes like -5i to the bottom of zero.