| rabio | enrage, rabid, rage |
| racemus | raceme, raisin |
| radius | irradiate, radial, radiance, radiant, radiantly, radiate, radiation, radiator, radio, radium, ray, rayon |
| radix | eradicate, horseradish, radical, radicalism, radically, radish |
| rado | erase, eraser, raze, razor |
| ramus | ramification |
| ranceo | rancid, rancor, rancorous |
| rapio | enrapture, rapacious, rapaciousness, rapacity, rape, rapid, rapidity, rapidly, rapids, rapine, rapt, rapture, rapturous, ravage, ravenous, ravin, ravine, ravish, ravisher, ravishing |
| rarus | rare, rarely, rareness, rarity |
| ravis | raucous |
| recens | recent, recently |
| reciprocus | reciprocal, reciprocate, reciprocation, reciprocity |
| reclino | recline: s. also declino and inclino |
| refuto | refutation, refute |
| rego | address, adroit, adroitly, adroitness, alert, alertly, alertness, correct, correction, corrective, correctly, correctness, direct, directory, dirge, dirigible, dress, dresser, dressmaker, dressmaking, dressy, drest, erect, erection, escort, hairdresser, headdress, incorrect, incorrigible, indirect, indirectly, insurgent, insurrection, irregular, irregularity, irregularly, misrule, overrule, rail, railing, railroad, railway, rectangle, rectangular, rectify, rectitude, rectory, redress, regency, regent, regime, regimen, regiment, regimental, region, regional, regular, regularity, regularly, regulate, regulation, regulator, resource, resourceful, resourcefulness, resurrection, rule, ruler, source, surge, undress, unruly |
| religio | irreligious, religion, religious, religiously |
| reor | arraign, arraignment, irrational, overrate, rate, ratification, ratify, rating |
| repo | reptile |
| repudium | repudiate, repudiation |
| res | real, realism, realist, realistic, reality, realization, realize, really, realty, republic, republican, unreal, unreality |
| resina | resin, resinous, rosin |
| restauro | restaurant, restoration, restorative, restore, restorer; s. also instauro |
| rete | retina |
| retro | arrears, rear |
| rex | realm, regal, regicide, reign, royal, royalist, royally, royalty, viceroy |
| rideo | deride, derision, derisive, derisively, ridicule, ridiculous, ridiculously |
| rigeo | rigid, rigidity, rigidly, rigorous, rigorously |
| rigo | irrigate, irrigation |
| ripa | arrival, arrive, river, riverside |
| ritus | rite, ritual |
| rivus | derivation, derivative, derive, rival, rivalry, rivulet, unrivaled |
| robur | corroborate, corroboration, robust |
| rodo | corrode, corrosive, erosion, rodent |
| rogo | abrogate, arrogance, arrogant, derogate, derogation, derogatory, interrogate, interrogation, interrogative, prerogative, rogation, surrogate |
| Roma | romance, romancer, romantic, romanticism |
| ros | rosemary |
| rosa | rosary, rose, roseate, rosebud, rose-colored, rosette, rosewood, rosy |
| rota | around, comptroller, control, controller, enroll, enrollment, merry-go-round, rigmarole, rondo, role, roll, roller, rolling |
| rudeo | rouge, rubric, ruby |
| rudis | erudite, erudition, rude, rudely, rudeness, rudiment, rudimentary |
| ruga | corrugate, corrugated |
| ruman | ruminant, ruminate, rumination |
| rumpo | abrupt, abruptly, bankrupt, bankruptcy, corrupt, corrupter, corruptible, corruption, disrupt, disruption, eruption, eruptive, incorruptible, interrupt, interruption, irruption, route, routine, rupture, uncorrupted, uninterrupted |
| ruo | ruin, ruinous |
| rus | rural, rustic, rusticity |
| russus | russet |
