0 is a real number.
No. The square root of negative one is an example of an imaginary (not real) number. Pi is irrational, but real.
2 is a real world prime number.
It need not be. For example, a complex number as a percent of most other complex numbers, or any real number, will not be a real number.
2.5 is an example.
It is a real number because for example water freezes at 0 degrees Centigrade
the square root of 2
One-eighth
The square root of 2 is real number but it is not rational number because it can't be expressed as a fraction.
Any odd root, for example the cube root, of -3.24 is a real number.
pi, or the square root of 2.
Euler's number, e = approx 2.71828