Why aren't python nested functions called closures?

Question

I have seen and used nested functions in Python, and they match the definition of a closure. So why are they called nested functions instead of closures<

Answer 1

Python 2 didn't have closures - it had workarounds that resembled closures.

There are plenty of examples in answers already given - copying in variables to the inner function, modifying an object on the inner function, etc.

In Python 3, support is more explicit - and succinct:

def closure():
    count = 0
    def inner():
        nonlocal count
        count += 1
        print(count)
    return inner

Usage:

start = closure()
start() # prints 1
start() # prints 2
start() # prints 3

The nonlocal keyword binds the inner function to the outer variable explicitly mentioned, in effect enclosing it. Hence more explicitly a 'closure'.