"$X$" with an "$n$" in the bottom right: what is it called and how do I type it?

Question

From time to time, i have come across the symbol x with a little n in the bottom right, similar to aleph numbers. What is it called, and how do I type it?

Answer 1

Do you just mean a subscript? E.g. $a_1$, $a_2$, ..., $a_n$.

They are called subscripts. You can say "a subscript 1", "a sub 1" or, if the context is obvious, just "a 1".

It is easy to type those in MathJax. They should surrounded by \$ signs as usual. For $a_1$, I used a_1. If the subscript is more than one character, you need to use { and }. E.g. $a_{i_1}$ for which I used a_{i_1}.

Superscripts (e.g. exponentiation) are similar but use ^ in place of _. E.g. For $a^2$ I used a^2. Again, use { and } if there is more than one character e.g. $a^{x + y}$ is a^{x + y}.