To (slightly) oversimplify, syntax deals with the ordering of words.
What, on the other hand, deals with the ordering of letters?
EDIT: Some word OTHER THAN spelling, which apparently to SOME people is ALSO neither prescriptive nor descriptive outside of context. Well, to me it almost ALWAYS implies some degree of prescriptivism and so I'm not looking for that word. Even it you think it is the solution to this question, I'm changing the question to exclude it. It's not the word I'm looking for.
EDIT 2: Okay, people, you're wayyyy overthinking this. (This is why I don't go on SE much; people tend to be over-specific...) It isn't at all unclear what I'm asking. It's simple: what word, other than spelling, serves the same purpose as the word syntax, but for the ordering of letters rather than the ordering of words?