Three Words That Have Never Been Improved

"Mind the gap."

You've heard it — clipped, recorded, faintly disapproving — a thousand times on the London Underground, and you have never once misunderstood it. That is a small miracle, and the miracle is grammatical.

Start with the verb. Mind. Not "be aware of," not "please take care regarding," not "caution." Mind — an old, plain, slightly stern little verb meaning attend to this, or regret it. It does the work of an entire safety notice in four letters.

Then notice what isn't there. No subject. "Mind the gap" is in the imperative mood — the one mood in English that never bothers naming who it's talking to, because it's talking to you and you both know it. Spelling it out ("You should mind the gap") would only slow you down at the precise moment you haven't got one to spare.

And the gap — not a gap, not any gap. The definite article quietly assumes you already know which gap we mean. Of course you do. There's only ever one that matters, and it's the one between you and the train.

Three words: one verb, one article, an invisible subject, and a warning you've absorbed before you've finished reading it. They could have written a paragraph. Somebody, mercifully, wrote this instead.

Well played.

The imperative — and the other moods a verb can stand in — is Pillar 4, the verb system.