They're languages, or notations. Like https://en.wikipedia.org/wiki/Notation_for_differentiation https://en.wikipedia.org/wiki/Notation_for_differentiation the

They're languages, or notations. Like https://en.wikipedia.org/wiki/Notation_for_differentiation https://en.wikipedia.org/wiki/Notation_for_differentiation there's different schools of thought on what's easiest to read, while the fundamentals are essentially the same. Calculus is a tool, but how we write it is just the notation. Similarly, computer programming (or perhaps a subfield like functional programming) is the tool, and a particular language is just the notation for writing it down.