In language, there are grammar rules, and then there are styles. Let’s consider, for example, using a series in a sentence.
English grammar says that a series ought to be parallel.
Don’t write this: Laine signed the contracts, the time sheets, and wrote his name on the paychecks.
Do write this: Laine signed the contracts, the time sheets, and the paychecks.
Then style comes into play. Oxford style says a comma should come before the last item in a series.
Laine signed the contracts, the time sheets, and the paychecks.
Associated Press style says that the final comma is unnecessary.
Laine signed the contracts, the time sheets and the paychecks.
So certain rules change according to which style you are following. Easy enough, you might say. Just use the right manual.
The trouble is, however, that grammar itself doesn’t have a rule for every situation. At the very least, some rules are obscure.
Consider, for example, the situation described in “My Big Fat Greek Blog Post.” Never in my education as an English major did anyone ever teach that adjectives are placed in order of opinion, size, age, shape, color, origin, material, and purpose. Nor does the possessive adjective “my” fit any of those categories.
Such gaps become most evident when teaching a language to non-native speakers. One of my daughters teaches English to adults in Belgium. Recently, her students asked which of these is correct: “A friend of Mary’s” or “A friend of Mary.” She suggested that both are correct and mean the same thing, but the first puts a slightly greater emphasis on Mary.
Then the students changed one word. What about “A photo of Mary’s” versus “A photo of Mary”? In this case, of course, the meanings are entirely different. Depending on what they wanted to say, the students would have to choose one phrase or the other.
At times like these, grammarians are forced to invent a rule to describe (or fit) the situation. In a way, such scenarios define grammar—a set of rules describing how people use language. The language comes first; the description comes second. And style trails along after that.