This book provides various aspects of The Theory of probability written in a simple and lucid style to help the reader grasp the information quickly and easily. The book contains 11 chapters and each chapter present update material sufficient to meet the students expectations from a basic textbook.This book aims to give an exposition of the fundamentals of the theory of probability, a mathematical science that treats of the re-gularities of random phenomena.Today, probability theory is extending its influence and practical application to many spheres, and researches throughout the world have enriched the theory with important results.