What is a keyword in programming?

A keyword in programming refers to a reserved word that has a specific meaning within the programming language syntax. Keywords are fundamental elements that define the structure and behavior of the code, serving as the building blocks for commands, declarations, and structure.

For example, in many programming languages, keywords are used for control flow (like "if", "else", "while"), data types (such as "int", "float"), and other critical functionalities that dictate how the program operates. Since keywords are built into the programming language, they cannot be used as identifiers for variables or other user-defined elements.

This definition distinguishes keywords from other programming concepts, such as variables, which can hold changing data; external libraries, which are additional pieces of code that extend functionality; and comments, which provide explanatory notes within the code but do not affect its execution. Thus, the identification and proper use of keywords are crucial for effective programming.