You have been using functions since your first program: print, input, len, round. A function is a named piece of code that does a job. Now you will make your own, with def (short for define):

def say_hello():
    print("Hello!")
    print("Welcome to the course.")

say_hello()
say_hello()

The def block doesn't run anything by itself: it teaches Python a new command. The code inside only runs when you call the function by writing its name with brackets, say_hello(). Call it twice and it runs twice.

The shape is familiar: def, a name, brackets, a colon, and an indented block underneath. Function names follow the same rules as variable names, and by convention describe an action: say_hello, draw_box, work_out_total.