The subject area of probability is actually expressed as a fraction or percentage because it represents a part of a whole. In lay man's term, probability is the scientific study of chance, likeliness and odds of an event happening. For example, you want to find the odds of getting a heads in a toss of the coin. You know that there are 2 possible results: head and tails. So, the probability of getting a head is 1/2 or 50%. Since it is a part of a whole, the probability in fraction should never be an improper fraction. This is the type of fraction in which the numerator is greater than the denominator. This is impossible as a probability because it will never exceed 1.