Repeating technical terms using varied ones
I wrote an answer for the question pre-edit, addressing more than just the question of synonyms. Hopefully it can be of wider use, as it provides references to other resources, and an overall principle that helps answer many questions about writing. Here it goes.

I once took a course in technical communication, which was largely based on an excellent textbook by Paul V. Anderson called Technical Communication: A reader-centered approach. It is perhaps a bit more targeted to technical communication in the private sector than academia, but it has many helpful hints, examples, and rules of thumb. However, the main principle Anderson repeatedly states is reflected already in the title: focus on the audience. Before writing a document or preparing a talk, think through what audience you're targeting, and then adapt the order things are presented in, terminology, notation, depth of the introduction etc. based on that. 

This also applies on the level of paragraphs. If sentences are put in a logical order, the text flows better and makes more sense. Similar considerations apply also on the microlevel - e.g. using various synonyms for technical terms is likely to confuse the reader more than it helps, so it should be avoided, especially if different synonyms can mean other things in adjacent fields. Also avoid phonetically confusing notation, such as using 'new' as a subscript. Very long sentences can make the text harder to understand, so the author should ideally try to rework them. Other times they are the clearest way of expressing a given idea you can come up with, which is also fine. Now, it is hard to find the perfect balance the first time around, which is where editing comes in. Edit both for correctness, and to iteratively make the text more readable. (If you know programming, this process is a bit like refactoring code.) If possible get feedback from others (maybe you don't know your audience as well as you think!), and edit accordingly.

Since you've been active on the physics stack, I would also like to point you towards David Mermin's writings on the art of writing. I first read them when I was writing my own masters thesis, and had several 'aha!' moments, including about how to think about equations grammatically. They are also quite enjoyable to read, so I do like sharing them.


What's Wrong with this Prose? (non-paywall version)
What's Wrong with these Equations? (non-paywall version)
Writing Physics


For mathematical writing you'll find further references in Good books/resource on mathematical writing. Also see How to improve technical writing and links therein.