orthography (n.)

mid-15c., ortographie, ortografie, "branch of knowledge concerned with correct or proper spelling," from Old French ortografie (13c.), from Latin orthographia, from Greek orthographia "correct writing," from orthos "correct" (see ortho-) + root of graphein "to write" (see -graphy). The classical spelling was restored in English and French (orthographie) in early 16c.  The meaning "branch of language study which treats of the nature and properties of letters" is from 1580s. Related: Orthographer.