What is the proper way to read subscripts in Mathematics?

[GPhab]

What is the proper way to read subscripts in Mathematics? Sometimes we come across functions with two arguments, where one of them is indicated using subscripts and in such situations, there is scope for confusion.
Eg:$$L_n$$(X) can be confused with Ln(X)
We can produce many more examples like this

 

[quasar987]

I suppose you mean $$L_n(X)$$ can be confused with $$Ln(X)$$

 

[quasar987]

one is imply Ln, the other is "L sub n" or "L index n"

 

[CompuChip]

Also, when $$Ln(x)$$ refers to the logarithm (natural base) it is usually written upright, as in $$\ln(x)$$ or $$\operatorname{Ln}(x)$$. Usually, only certain standard functions have more than one letter, at least, I rarely call my functions other than $$f(x), \phi(z), \Psi(\vec r), \cdots$$, never fn(x), crv(x, y, z) or wf(r)

[edit]I just consciously read the topic title -- my above post doesn't really make sense does it?
In your example, if I had to read the equation out to someone and confusion might arise, I'd probably use "L sub n" for one and "log" for the other.
[/edit]

 

[Gib Z]

I actually say out the whole thing, it irritates all my friends >.< Eg $$\frac{d}{dx} f(x)$$. My friends say "dee- dee x, eff, x" and i say "The derivative of eff x with respect to x". For this example it would be "The Natural Logarithm of x" as opposed to "The function L sub n, evaluated at x".