Here is a more generic form for the definition of limit of a function at a point.

Notice that I have jammed both of the phrases "neighborhood E of L" and "neighborhood D of the point a".

I have also jammed "x belongs to D" and "f(x) belongs to E".

Note that "f(x)" will be vulerable to parsing, hence I write it as "f of x" inside the jammed form.

Unfortunately the "then" in the last clause got mangled by the parser.