There are three out of four binary classification metrics mentioned in the Book of Why; true positive, false positive, and false negative. The fourth one that is not mentioned in the book is true negative. The following are the two primary building blocks of such four metrics:

1. True vs. False: These are about prediction's correctness whether a prediction outcome was made accurately/ correctly. The correct prediction is True, and the incorrect prediction is False.
2. Positive vs. Negative: These are about a binary classification -(e.g.) In the mammogram example in the book, "positive" is positive test results (breast cancer), whereas "negative" is negative test results (not breast cancer).

The combinations of the above concepts result in True positive, True negative, false positive, and false negative, each of which is explained in the subsequent nodes to follow.