What Is Probability?
What Is Probability?
A probability is a measure of how likely (how probable) an event is to happen.
A probability is expressed as a number between 0 (impossible) and 1 (certain).
Dictionary Definition
The Oxford English Dictionary defines a probability as "the extent to which a particular event is likely to occur... expressed by a number between 0 and 1.
The Probability Scale
Probabilities express how likely an event is to happen on a scale of 0 to 1.

An event with a probability of 0 is impossible: it cannot happen.

An event with possibility of 1 is certain: it will happen.
As a probability is closer to 0, the less likely an event is to happen.
As a probability is closer to 1, the more likely an event is to happen.
Expressing Probabilities
A probability can be expressed as:

a number between 0 and 1.

a fraction.

a percentage between 0% and 100%.