According to Wikipedia, a [monotonic function](https://en.wikipedia.org/wiki/Monotonic_function) is a function that is either increasing or decreasing. If a function is increasing and decreasing then it's not a monotonic function or it's an *anti-monotonic* function. 

But the data mining book, "Data Mining: Concepts and Techniques," describes *anti-monotonic* property as: If a set is infrequent then all of its supersets are also infrequent.

Doesn't this property look the same as monotonic according to Wikipedia? What is the difference between the two?