The book (mostly) uses the term 'monotony' rather than 'monotonicity'. To be honest, I've never encountered the former used as a synonym for the latter in mathematical contexts, although that may be my ignorance speaking more than anything. But since 'monotonicity' seems to be far more widely used, I suggest that we switch wholesale to the latter. I'm happy to author a commit making this change.
The book (mostly) uses the term 'monotony' rather than 'monotonicity'. To be honest, I've never encountered the former used as a synonym for the latter in mathematical contexts, although that may be my ignorance speaking more than anything. But since 'monotonicity' seems to be far more widely used, I suggest that we switch wholesale to the latter. I'm happy to author a commit making this change.