pass

The root pass begins with one small physical thing: a step. Latin passus meant "a step, a pace" — the distance covered when a Roman walker lifted one foot and set it down ahead of the other. (The Roman "pace" was actually a double step, and a thousand of them — mille passus — gave us the word mile.) passus itself was the past participle of pandere, "to spread out, stretch" — because to take a step you stretch your legs apart.

From "a step" came two everyday English words almost unchanged: pace kept the idea of how fast or how far you step (a slow pace, pick up the pace), and pass absorbed the idea of going — moving past, going through, getting by.

But the bigger family grew from a later, busier Latin verb: Vulgar Latin passāre, "to walk, to step, to go past." Once you have a verb for "going through," prefixes and combinations do the rest:

- passage — the going-through itself, and by extension the narrow place you go through (a corridor, a strait, a stretch of text you move through while reading).
- passenger — literally "one who passes through"; someone carried along on a journey while someone else does the driving.
- passport — pass + port (gate/harbor): the paper that lets you pass through the port. In the age of walled cities, you could not get past the gate without it.
- past — the most surprising member: it is simply the old participle of pass, "having passed." Time that has gone past is the past.
- surpass (sur- over) — to step over and beyond, to exceed.
- bypass (by- beside) — to step to the side of something and avoid it.
- overpass — a bridge that passes over a road.
- trespass (tres- across, from trans-) — to step across a line you shouldn't: in plain English, to enter where you don't belong.
- compass — the oddest cousin. com- (together) + passus = "to pace out together," to step around the full circle of something. That is why a compass can mean both the twin-legged drawing tool that paces out a circle and the navigation device that covers all directions — and why "the compass of a subject" means its full range or scope.

The thread through all of them is the same simple motion: a foot lifts, a step is taken, you go through or go past. Whether it is a traveler passing a border, a reader passing through a paragraph, or time passing into the past, every pass word is a step.