Extended Backus-Naur Form (EBNF) is a notation used to express the grammar of programming languages and data formats. It extends the original Backus-Naur Form (BNF) by adding additional syntax features, such as optional elements, repetitions, and grouping, making it more concise and easier to read. EBNF allows for clearer definitions of language constructs, enabling developers to specify rules for valid sequences of symbols. This helps in the design of compilers and interpreters, as well as in the documentation of programming languages, ensuring that the syntax is well-defined and unambiguous.