h₃reǵ-
“to straighten, to rule”straighten, direct, rule
Root for ruling/directing, yielding Latin rex/regere, English right, rich, rule.
Discussion
The PIE root *h₃reǵ- (to move in a straight line, to straighten, to direct) is one of the most politically and geometrically productive roots in the reconstructed vocabulary. The laryngeal is debated — some scholars reconstruct *h₁reǵ- — but the root's reflexes are among the most secure in comparative linguistics.
Latin rēx (king — genitive rēgis, "the one who directs") and the verb regere (to guide, to rule, to keep straight) generated an enormous English vocabulary: regal, regent, regime, regiment, region, regulate, reign, and the vast rectus family — rector, rectify, correct, erect, direct, and rectangle. English right (OE riht, from PGmc *rehtaz) descends from the same root through Germanic, making right a native cousin of Latin rēx.
Sanskrit rā́jan- (king) and the related rāj- (to rule) continue the root in Indo-Iranian — Maharaja ("great king") and the British Raj are direct descendants. Celtic preserved the root in Gaulish -rīx (as in Vercingetorix) and Old Irish rí (king).
The root encodes a political philosophy in its etymology: legitimate authority IS straightness, proper rule IS the maintenance of a straight line. When English speakers say "that's right" they invoke a PIE concept of cosmic straightness that also named their kings.
Notes
Pokorny 854-857. English right, regal, reign, rector, regime.
Related Roots
English Words from *h₃reǵ-
These modern English words descend from this root. Each page traces the full journey from PIE to present-day English.