Can the phrases "is equal to" and "equals" be used interchangeably? I found a duplicate to this question in the English StackExchange.
https://english.stackexchange.com/questions/71259/is-equal-to-or-equals
I see these two phrases a lot in the context of mathematics. They seem interchangeable, but I cannot be sure, because I'm not well acquainted with English or maths. Do you think they
are interchangeable? If not, in what circumstances do you prefer one to the other?
 A: Yes, they are interchangeable.
A: They are almost interchangeable; however, arguably, there are no true synonyms in natural language. Aside from a subtle change in register, there are specific contexts where one or the other sounds more natural to me, or where one is more ambiguous than the other.
For instance, "equals sign" is common across many countries with a large English-speaking population. But Google Trends suggests that "is equal to sign" seems to only have significant use in India, if anywhere.
On the other hand, consider "is-equal-to relation" (sometimes with quotation marks around 'is equal to' instead of hyphens). That phrase is always used to mean the particular equivalence relation $R$ given by "$aRb$ exactly when $a=b$". But at least one scientific dictionary* defined "equals relation" as "equivalence relation", in general. So there is, at best, more ambiguity with "equals relation". Personally, I don't think I have ever heard "equals relation".
*McGraw-Hill Dictionary of Scientific & Technical Terms, 6E
