What keyword is used to define a function in Python?

In Python, the keyword used to define a function is "def." This keyword is essential as it signals the start of a function definition, followed by the function name and parentheses that may include parameters.

When you write a function in Python, you begin with "def" to inform the interpreter that what follows is a function. This is part of Python's syntax rules, which dictate how functions must be declared in the language. For example:

def my_function(parameter1, parameter2):

# Function body

return parameter1 + parameter2

In this example, "def" indicates that "my_function" is being defined, and it takes two parameters. Without using the "def" keyword, the interpreter would not recognize that you are trying to define a function, leading to a syntax error.

The other options, such as "function," "define," and "func," might suggest some form of function declaration, but they are not valid keywords in Python for this purpose. Therefore, the use of "def" is crucial for function definitions in Python.