"Semantics with Applications: An Appetizer" is a technical book that explores the role of semantics in the development of software systems and domain-specific languages. It provides an introduction to the fundamental concepts of semantics and their applications in computer science. The book formulates and proves relevant theorems and demonstrates how these concepts can be applied in various fields. It highlights both historically significant and forward-looking applications, such as the validation of programming language prototypes, the verification of program analyses and security analyses, as well as the verification of useful program properties, including information on execution time. The clear structure and illustrative examples make it a valuable entry point into the topic of semantics.