HAPPY National Grammar Day, everyone. Today's offering is only marginally on grammar. We've asked "What is grammar anyway?" here at Johnson. The layperson would almost certainly answer "those difficult rules that are drilled into you in school about how to use the language." The linguist would reply with nearly the opposite: grammar is made up of the rules of language that a competent native speaker uses almost without effort, by the definition of "competent native speaker". You use grammar every time you construct a sentence, not just those times when you're scratching your head about whether to use "who" or "whom".

Here's a good example of how laypeople and linguists differ on grammar: OnlineSchools.com has created this handy infographic on the much-discussed punctuation mark known as the Oxford comma.

To recap, the Oxford comma separates the last two items in a list, as in "red, white, and blue". For reasons opaque, the use or non-use of the final comma here stirs passions all out of proportion to its importance. As OnlineSchools.com's graphic notes, much of the world uses it, but equally respectable publishing houses and publications do not. The Economist is in the latter camp: we would write "red, white and blue". Defenders of the Oxford comma point to an almost certainly apocryphal story of the student who dedicated a piece of work to "my parents, God and Ayn Rand". But anyone who writes such a thing has bigger problems than punctuation. Any sensible person would edit and remove such messes as this, whether they use the Oxford comma or not.

What I like about OnlineSchools.com's graphic is its explanation that the Oxford comma isn't a black-or-white, always-or-never thing. It is a matter of style. Use it or don't, but be consistent, and you're fine. Rarely is such finesse on display when people talk about these things.

Are commas even grammar? For many people, the idea that they aren't might be ludicrous. But language scholars by and large think of punctuation (whether to use the Oxford comma; whether to put commas and full stops inside inverted commas or outside) as orthography or mechanics, not grammar. Punctuation is useful for organising prose to make it readable. But these squiggles are not at the heart of how words are built from smaller pieces (like adding -ed to make the past tense) or making sentences from words (like using "whom" as an object in certain clauses).

So on National Grammar Day, some traditionalists will complain that no one seems to know how to use commas (and apostrophes and dashes) anymore, while most linguists will insist that this is the small stuff, and not even really grammar. It's refreshing that this is an ongoing debate. One of the things we should agree on about grammar is that while it's important, it isn't always easy, and the right answer isn't always clear.