What does "n" stand for in n-akyldiols, n-alkanes, n-dicholoroalkanes?
The "n" stands for "normal", which in this context means "straight-chain".  It is not italisized, since it is not Latin, but English.  In contrast, the prefixes "i" or "a" for "iso" and "anteiso" are Latin and are properly italisized, but rarely are.  

Your second choice, "n is like x", can be found in the subscripts of chemical formulae, where it does denote a variable amount.