What is a function in programming?

A function in programming is correctly defined as a reusable block of code that performs a specific task when called. This encapsulation of code allows programmers to define a sequence of operations once and then execute it multiple times throughout a program without rewriting the same code. Functions promote modularity, making programs easier to manage, understand, and debug.

When a function is invoked, it can take input parameters, execute its code, and often return a value. This allows for flexibility, as the same function can be reused with different inputs to achieve different results. The ability to reuse code through functions not only saves time but also reduces the chances of errors since well-tested functions can be relied upon throughout a codebase. Functions are a fundamental concept in programming that enhances code organization and readability.

The other options focus on concepts unrelated to the core definition and purpose of a function. For example, a variable is a storage mechanism for values, syntax rules pertain to the grammar of programming languages, and comments are used for documentation rather than defining functions. Understanding the primary role of functions is crucial in mastering programming and writing efficient code.