Usually this is called pure mathematics, as opposed to applied mathematics. On the other hand, applied mathematics might also involve some pretty technical "th

Usually this is called pure mathematics, as opposed to applied mathematics. On the other hand, applied mathematics might also involve some pretty technical "theoretical maths", which though being applied, can be studied for its own interest without the application. So in some sense, "applied maths" sometimes means maths that is applied, rather than maths that can be applied. For that reason it perhaps makes sense to instead use the term "theoretical maths", though I am not sure if that is standard terminology or not.