The textbook "Triangular Norms" offers a comprehensive examination of the theory of triangular norms, which originated from the work of Karl Menger. Menger developed the idea of constructing metric spaces where probability distributions are used instead of numbers to describe the distance between elements. This book addresses the development and fundamental axioms of t-norms, which play a crucial role in the theory of probabilistic metric spaces. The authors, Berthold Schweizer and Abe Sklar, formulated the axioms of t-norms that are still in use today. The monograph summarizes many results achieved throughout the development of t-norms and provides deep insights into the mathematical foundations of this theory. The connection between functional equations and special topological semigroups is also discussed, highlighting the relevance of t-norms in various mathematical disciplines.