reg- / Indo-European roots
Examples of words with the root reg-: abrogate, anorectic, anorexia, arrogate, bishopric, correct, corvée, derecho, derogate, direct, eldritch, erect, ergo, interrogate, maharaja, maharani, prerogative, prorogue, rack, rail, raita, raj, raja, rake, rank, real, realm, reck, reckless, reckon.
To move in a straight line, with derivatives meaning "to direct in a straight line, lead, rule." Oldest form *h3reg̑-, becoming *h3reg- in centum languages.
▲ Derivatives include right, realm, anorexia, rich, rule, interrogate, reckless.
I. Basic form *reg-.
1. Suffixed form *reg-to-. right from Old English riht, right, just, correct, straight, from Germanic *rehtaz.
2. realm, rectitude, recto, rector, rectum, rectus, regent, regime, regimen, regiment, region; address, adroit, alert, correct, derecho, direct, erect, incorrigible, porrect, rectangle, rectify, rectilinear, resurge, Risorgimento, sord, source, surge from Latin regere, to lead straight, guide, rule (past participle rēctus, hence adjective rēctus, right, straight).
3. orexin; anorectic, anorexia from Greek oregein, to stretch out, reach out for (with o- from oldest root form *ə3reg̑-).
II. Lengthened-grade form *rēg-, Indo-European word for a tribal king.
1. a. bishopric, eldritch from Old English rīce, realm; b. Riksmål from Old Norse rīki, realm; c. Reich; reichsmark from Old High German rīchi, realm; d. rich from Old English rīce, strong, powerful, and Old French riche, wealthy. a-d all from Germanic *rīkja-, from Celtic suffixed form *rīg-yo-.
2. real2, regal, regulus, reign, rex, rial1, riyal, royal; ariary, regicide, regius professor, vicereine, viceroy from Latin rēx, king (royal and priestly title).
3. Suffixed form *rēg-en-. raj, rajah, rani, rye2; maharaja, maharani from Sanskrit rājā, rājan-, king, rajah (feminine rājñī, queen, rani), and rājati, he rules.
III. Suffixed lengthened-grade form *rēg-olā-. rail1, reglet, regular, regulate, rillettes, rule from Latin rēgula, straight piece of wood, rod.
IV. O-grade form *rog-.
1. rake1 from Old English raca, racu, rake (implement with straight pieces of wood), from Germanic *rakō.
2. rack1 from Middle Dutch rec, framework, from Germanic *rak-.
3. Possibly Germanic *rankaz (with nasal infix) rank2 from Old English ranc, straight, strong, hence haughty, overbearing.
4. reckon from Old English gerecenian, to arrange in order, recount (ge-, collective prefix; see kom) , from Germanic *rakinaz, ready, straightforward.
5. Suffixed form *rog-ā-. rogation, rogatory; abrogate, arrogate, corvée, derogate, interrogate, prerogative, prorogue, subrogate, supererogate from Latin rogāre, to ask (< "stretch out the hand").
6. Suffixed form *rog-o-. ergo from Latin ergō, therefore, in consequence of, perhaps contracted from a Latin phrase *ē rogō, "from the direction of" (ē, < ex, out of; see eghs) , from a possible Latin noun *rogus, "extension, direction"
V. Lengthened o-grade form *rōg-.
1. reck from Old English rec(c)an, to pay attention to, take care (formally influenced by Old English reccan, to extend, stretch out, from Germanic *rakjan), from Germanic *rōkjan.
2. reckless from Old English rēcelēas, careless (-lēas, lacking; see leu-) , from Germanic rōkja-.
VI. Suffixed zero-grade form *r̥g-yo-. raita from Sanskrit ṛjyati, he stretches out.
[Pokorny 1. reg̑- 854.]