Is there a syntax reference for math, like for programming languages?

Different branches of mathematics develop their own notation, so there isn’t _a_reference_, there _are_references_, just like there are for programming languages.

Also like with programming languages, there are communalities that are valid most of the time. Simple examples that you probably know are the way we write numbers, using + for addition, using {} to denote sets, ℝ for the real numbers, etc.

You’ll find that many math books start with an overview of the notation used.

https://en.wikipedia.org/wiki/History_of_mathematical_notati... mentions tons of specialized notations (most of which, I guess, you won’t need to know about)

Mathematics use written languages, they're not programming languages. The syntax is not fixed and depends on context and the author. It's not uncommon for new ideas to introduce new syntax.

Most of this is explained through coursework and instruction in the relevant domains where when you hit something you don't understand you ask your mentor/teacher/colleague/the original author what something means.