Algebraic Number Theory 2: Basic Definitions from Commutative Algebra

In this video I recall some basic definitions from commutative algebra. This is from Chapter 1 Section 1 of Milne's notes at:

[derrikgratz]

Love this channel. Best Algebraic number theory videos on the web.

[kdr]

I always find difficult to check or prove “well-defined”. Could you help me explain the Pi star is a well-defined bijection? Thank you so much.

[justingreenough]

I really want to sit through this, I do. The writing out of every word with the mouse though is very inefficient.