python初心者です。参考書通りだと思うのですがname 'square' is not definedと出てしまいます

"""
Module documentation
words go here
"""
spam=40
def spuare(x):
    """
    function documentation
    can we have your liver then?
    """
    return (x**2)

class employee:
    "class documentation"
    pass
print (square(4))
print (square.__doc__)

Traceback (most recent call last):
  File "docstrings.py", line 16, in <module>
    print (square(4))
NameError: name 'square' is not defined

(Python 3.7.3 (v3.7.3:ef4ec6ed12, Mar 25 2019, 22:22:05) [MSC v.1916 64 bit (AMD64)] on win32)