diameter

Where does the word "diameter" come from? It comes from Greek dia, passing through Latin and Old French before entering English (1300s).

Diameter’s story begins in Greek: dia meant “through, across.” Through, across, combined with metron (measure). By ancient, the word had taken hold in Latin as diametrus. Carried into Latin for the line measuring across a circle. From there it passed into Old French as diametre by medieval. Carried into French for the same measurement. It reached English by 1300s as diameter. Settled as the English word for the measurement across a circle. Today, diameter means a straight line passing through the center of a circle, connecting two points on its edge.

1. Stage 1 · Greek · ancient dia "through, across", through, across, combined with metron (measure).
2. Stage 2 · Latin · ancient diametrus "the line measuring across a circle", carried into Latin for the line measuring across a circle.
3. Stage 3 · Old French · medieval diametre "the measurement across a circle", carried into French for the same measurement.
4. Stage 4 · English · 1300s diameter "the straight line measurement across a circle", settled as the English word for the measurement across a circle.