What keyword is used to define a function in Python?

The keyword used to define a function in Python is "def." When you want to create a function, you start with the "def" keyword followed by the function name, parentheses, and a colon. This signal initiates the function's definition, allowing you to include the necessary code block that will execute whenever the function is called.

Using "def" is a fundamental principle in Python programming, marking the start of function declaration and allowing the function's scope and properties to be clearly defined. This syntax is critical for organizing code, enabling reuse of functionality, and improving code clarity and maintenance.

The other keywords like "function," "func," and "define" do not have any special significance in the context of defining functions in Python and are not recognized by the interpreter for this purpose.