Recursion is a programming technique where a function calls itself during its execution. It is a fundamental concept in Lisp and many other programming languages. In a recursive function, the function breaks down a complex problem into smaller, simpler instances of the same problem until it reaches a base case that can be solved directly. The function then combines the results from the smaller instances to solve the original problem.

Lisp is particularly well-suited for recursion due to its flexible and expressive nature. Here are a few reasons why recursion is commonly used in Lisp:

1. Symbolic Processing : Lisp's ability to represent and manipulate code and data as symbolic expressions allows for elegant and natural recursive programming. The recursive structure of Lisp code can closely mirror the recursive nature of the problem being solved, leading to concise and readable solutions.

2. List Manipulation : Lists are a fundamental data structure in Lisp, and recursive techniques are often used to traverse and manipulate lists. Recursive functions can be used to process elements of a list one by one, either individually or in combinations, allowing for powerful and flexible list processing operations. 3. Tree Structures : Many problems involve tree-like structures, such as hierarchical data representations or recursive data structures. Recursion provides a natural way to traverse and operate on such structures. Lisp's recursive capabilities make it well-suited for tasks like tree traversal, searching, and transformation.

4. Divide and Conquer : Recursive algorithms often follow a "divide and conquer" approach, where a problem is divided into smaller subproblems that are solved independently. Lisp's support for recursion allows for the straightforward implementation of divide and conquer strategies, leading to efficient and modular code.

5. Code Reusability : Recursion promotes code reusability by allowing functions to be defined once and applied to multiple instances of a problem. Recursive functions can be written in a generic manner, making them suitable for a wide range of input sizes and problem variations.

6. Iteration Replacement : In Lisp, recursion can be used as an alternative to explicit iteration constructs like loops. Recursive functions can achieve similar outcomes as iterative loops while providing a more declarative and abstract representation of the problem.