What is Rational Numbers? - Definition Facts and Examples Examples of Rational Numbers. 4 5, − 10 15, 9 − 17, − 2 − 7. Zero is a rational number as we can write 0 can be written as 0 10, 0 2, 0 − 15, 0 27 etc. So, zero can be expressed as a fraction with a non-zero denominator. Every natural number is a rational number. 1 = 1 1, 5 = 5 1, 8 = 8 1.