Final answer:
A rational number can be expressed as a fraction with integers in both the numerator and the denominator or as a ratio. A fraction or ratio signifies a part of a whole or the relative size of one quantity to another. Rational numbers include fractions, ratios, scientific notations of such numbers, and exact numbers.
Step-by-step explanation:
A rational number is indeed a number that can be expressed as a fraction or ratio, having integers for both its numerator and its denominator. A fraction is written as a/b, where a is the numerator and b is the denominator (and b is not zero). This represents a part of a whole. Moreover, any number that can be expressed in this form where the numerator and denominator are integers and the denominator is non-zero is considered a rational number.
As for ratios, they tell us the relative size of one quantity to another and can also be expressed as fractions or percentages. When in fraction form, a ratio still conforms to the definition of rational numbers, with both terms being integers.
It's also important to note that not all fractions are rational numbers; only those with integers in both the numerator and denominator qualify. However, fractions represented in scientific notation or as exact numbers can also be rational.