The book "Applied Semi-Markov Processes" offers a comprehensive introduction to the application of semi-Markov processes to real-world problems. It is aimed at readers who wish to progress from basic concepts of probability to a deeper understanding of these processes. The content is structured in a way that builds step by step, covering both homogeneous and non-homogeneous semi-Markov processes. Additionally, Markov and semi-Markov reward processes are also introduced. The clear and systematic presentation of the concepts makes this book a valuable resource for students and professionals looking to engage with these important mathematical models. The thorough treatment of the topics sets it apart from other available literature and provides deeper insights into the subject matter.