Running Windows 10 python 3.8.1

[quark80]

I downloaded Python (3.8 64-bit)for Windows 10 & Windows Launcher, together with Manuals & Module Docs.
The 'sys.path' is set to C:\Users\quark\AppData\Local\Programs\Python\Python38.

Using: IDLE Python 3.8 64-bit:

While the usual math operators e.g +.-, *, ** , min() , etc. work, 'def' is not recognised and
math.pi generates:

"Traceback (most recent call last):
File "<pyshell#0>", line 1, in <module>
math.pi
NameError: name 'math' is not defined."

Can someone tell me how to rectify these errors?