How is the common syntax for a reference of points value?

Question

I just wonder how do I reference a value of a point in a widely accepted syntax.

For example there is the point $A(2\mid-6)$. How do I reference now the $x$-coordinate?

I would go for $A_x$ and $A_y$. What do you think?

Answer 1

That would be common-enough notation, for $2$ or $3$ dimensions (e.g. $A_x,A_y,A_z$).

Past that, (if, e.g. $A = (5,6,7,8,-2)$) you might use numbers as subscripts, e.g. $A_3 = 7, A_5 = -2$, etc.