Lisp is a programming language that was developed in the late 1950s and early 1960s as an attempt to provide a simple and flexible tool for artificial intelligence ([[AI]]) research. It is one of the oldest programming languages still in use today. Lisp has been influential in the development of functional programming, which is a programming paradigm that emphasizes the use of mathematical functions to perform computations. In Lisp, functions are first-class objects, meaning they can be assigned to variables, passed as arguments to other functions, and returned as results from functions. This allows for the creation of higher-order functions, which are functions that take other functions as arguments or return them as results. The relationship between [[Lisp]] and [[Lambda calculus]] is quite significant. Lambda calculus is a formal system developed by Alonzo Church in the 1930s to study the concept of computability and define mathematical functions. Lisp borrowed many concepts from lambda calculus, such as anonymous function literals (known as lambdas), function application through substitution, and recursion. Lisp's support for lambdas makes it a powerful language for expressing functional concepts. It allows programmers to define small, self-contained functions on the fly without needing to give them explicit names or declarations. This feature aligns closely with lambda calculus' focus on function abstraction and application. Additionally, Lisp's homoiconicity (the ability of code to be represented as data) enables metaprogramming capabilities that are often associated with functional languages. Programmers can manipulate Lisp code using built-in list processing operations, allowing for powerful macros that can transform and extend the language itself. Overall, Lisp's connection to lambda calculus has greatly influenced its design and functionality as a functional programming language. Its support for lambdas and its expressive power through metaprogramming have made it a popular choice among developers interested in functional programming paradigms.