This chapter provides a foundational introduction to probability, defining it as a mathematical measurement of the likelihood of random events. It structures the study of uncertainty by distinguishing between subjective probability, based on personal observation, and objective methods, which include experimental probability derived from data and theoretical probability based on ideal conditions. By utilizing a probability scale from 0 (impossible) to 1 (certain), the source teaches students how to quantify chance using tools like sample spaces, tree diagrams, and relative frequency. Ultimately, the text aims to dispel common misconceptions, such as the Gambler’s Fallacy, while illustrating how the Law of Large Numbers connects experimental results to theoretical expectations in everyday life.