Explain the role of recursion in syntax.

In computer science, recursion in syntax refers to a method used in programming languages and algorithms to handle nested or hierarchical structures. It allows a function or process to call itself in order to solve a problem, typically by breaking it down into simpler, similar sub-problems.

**Roles of Recursion in Computer Science:**

1. **Parsing Nested Structures**: Recursion is used in syntax parsing to handle nested constructs, such as nested parentheses or brackets in expressions. For instance, a recursive descent parser processes each level of nested structure by calling itself to handle substructures.

2. **Tree Data Structures**: Recursion is essential for manipulating tree structures, such as file directories or abstract syntax trees (ASTs). Operations like traversal, searching, and modifying trees often rely on recursive algorithms.

3. **Algorithms**: Many algorithms, such as those for sorting (e.g., quicksort, mergesort) or searching (e.g., binary search), use recursion to divide problems into smaller instances of the same problem until a base case is reached.

4. **Function Calls**: Recursive functions in programming can simplify code by allowing a function to call itself to solve sub-problems, making complex problems more manageable and code easier to read and maintain.

Recursion allows computer science to handle complex structures and operations efficiently by leveraging the principle of self-similarity, where a problem is solved by breaking it down into similar sub-problems.