what is the difference between MCC and WACC?

the curriculum’s explanation seems a little bit tricky.

Are these two terms interchangeable or has some different meaning somehow?

My understanding is that they are interchangeable.

Guys, ps. 36 of the Corp Fin book:

“The WACC is also referred to as the marginal cost of capital (MCC) because it is the cost that a company incurs for additional capital.”