Abuse of notation occurs in mathematics when a mathematical notation is used in a way that is not entirely correct, but that simplifies the expression or understanding of a particular concept. This is often done for the sake of brevity or clarity.

While the term "abuse" might suggest something negative, an abuse of notation is generally accepted in the mathematical community if it leads to less cumbersome notation or clearer understanding, and if it is unlikely to lead to any confusion or mistakes.

For example, one common abuse of notation is to write the differential dy/dx as a fraction, even though it is not truly a fraction but a limit of a ratio. This "abuse" simplifies the notation and understanding of many concepts in calculus.

Another example is the use of the same symbol to represent different things in different contexts. For instance, "f" might represent a function in one context, and a frequency in another. As long as it's clear from the context what "f" represents, this kind of abuse of notation is generally accepted.