Denotational semantics is a formal method for defining the meaning of programming languages. It assigns mathematical objects, called denotations, to phrases in a language, allowing for a precise understanding of their behavior. This approach focuses on the meaning of expressions rather than their execution, making it easier to reason about programs. In denotational semantics, each construct in a programming language is mapped to a specific mathematical structure, such as functions or domains. This mapping helps in analyzing and proving properties of programs, such as correctness and equivalence, by providing a clear and unambiguous interpretation of their semantics.