Words consist of units of meaning, called morphemes. These morphemes have a striking effect on spelling which has been largely neglected until now. For example, nouns that end in "-ian" are words which refer to people, and so when this ending is attached to "magic" we can tell that the resulting word means someone who produces magic. Knowledge of this rule, therefore, helps us with spelling: it tells us that this word is spelled as "magician" and not as "magicion."