|MOS was 71331|
When I try to use subscripts to distinguish variables in Mathematica, I get error messages (Subscript[x, 1] is not a symbol or a string.) telling me that I'm wrong to try. (I also get error messages when I use x1 rather than x_sub_1, but that's the subject of another thread in which I'm still awaiting an answer.)
Mathematica gives me easy ways to enter subscripts, Control-Minus from the keyboard and the second item on the left of the first row of the typesetting palette, but it doesn't tell me what I should use subscripts for.
What do subscripts mean to Mathematica?