| Same word of o.k., ok, okay | Same word of O.K., okay | Same word of oafish |
| Same word of oaken | Same word of obdurate | Same word of obdurate, obstinate |
| Same word of obedient (vs. disobedient) | Same word of obese | Same word of obey |
| Same word of obfuscate | Same word of object | Same word of objectify |
| Same word of objectionable | Same word of objectionable, obnoxious | Same word of objective |
| Same word of objective (vs. subjective) | Same word of objurgate | Same word of oblanceolate |
| Same word of obligate | Same word of obligate,oblige | Same word of obligated(predicate) (vs. unobligated) |
| Same word of obligatory | Same word of obligatory (vs. optional) | Same word of oblige |
| Same word of oblige, obligate | Same word of oblige,obligate | Same word of obliged(predicate) |
| Same word of oblique | Same word of oblique (vs. parallel) (vs. perpendicular) | Same word of oblique-angled |
| Same word of obliterable | Same word of obliterate | Same word of obliterate, obliterated |
| Same word of oblivious | Same word of oblivious(predicate) | Same word of oblong |
| Same word of obovate | Same word of obscene | Same word of obscure |
| Same word of obscure, obnubilate | Same word of obscure,obliterate | Same word of obscure,obnubilate |
| Same word of obsequious | Same word of observable | Same word of observant |
| Same word of observant, observing | Same word of observational | Same word of observe |
| Same word of observed | Same word of obsess | Same word of obsessed |
| Same word of obsessional, obsessive | Same word of obsessive-compulsive | Same word of obsolesce |
| Same word of obsolescent | Same word of obsolete | Same word of obstinate |
| Same word of obstipate | Same word of obstreperous | Same word of obstruct |
| Same word of obstruct, obturate, occlude | Same word of obstructed (vs. unobstructed) | Same word of obstructive |
| Same word of obtain | Same word of obtainable | Same word of obtrude |
| Same word of obtrusive | Same word of obtund | Same word of obtuse |
| Same word of obtuse | Same word of obviate | Same word of obviating(prenominal) |
| Same word of obvious (vs. unobvious) | Same word of occasion | Same word of occasional |
| Same word of occasional(prenominal) | Same word of occidental | Same word of occidentalize, occidentalise |
| Same word of occluded | Same word of occluded, | Same word of occult |
| Same word of occult,orphic | Same word of occupied | Same word of occupy |
| Same word of occur | Same word of occurrent | Same word of oceangoing |
| Same word of oceanic | Same word of ocher, ochre | Same word of octosyllabic |
| Same word of ocular | Same word of odd | Same word of odd-job(prenominal) |
| Same word of odd-pinnate | Same word of oddish | Same word of odds-on |
| Same word of odious | Same word of odoriferous | Same word of odoriferous, odorous |
| Same word of odorize, odourise | Same word of odorless (vs. odorous), odourless | Same word of odorous (vs. odorless) |
| Same word of oecumenic, oecumenical | Same word of oecumenical | Same word of of age(predicate) |
| Same word of of sound mind(predicate) | Same word of of the essence(predicate) | Same word of of unsound mind(predicate) |
| Same word of off | Same word of off (vs. on) | Same word of off the beaten track(predicate), out-of-the-way(prenominal) |
| Same word of off the hook(predicate) | Same word of off, off, polish off | Same word of off-and-on(prenominal) |
| Same word of off-base | Same word of off-center, off-centered | Same word of off-color |
| Same word of off-color, off-colour | Same word of off-guard(prenominal), off guard(predicate), off one's guard(predicate), off his guard, off her guard, off your guard | Same word of off-key |
| Same word of off-limits, out-of-bounds(predicate) | Same word of off-putting | Same word of off-the-rack, off-the-shelf, off-the-peg |
| Same word of off-the-shoulder | Same word of off-the-wall, outlandish, outre | Same word of off-white |
| Same word of offbea | Same word of offend | Same word of offend, offend |
| Same word of offend,outrage | Same word of offended | Same word of offenseless, offenceless |
| Same word of offensive | Same word of offensive (vs. defensive) | Same word of offensive (vs. inoffensive) |
| Same word of offensive (vs. inoffensive) | Same word of offer | Same word of offer, offer up |
| Same word of offer,oneself | Same word of offhand, offhanded | Same word of offhand, offhanded, off-the-cuff |
| Same word of officer | Same word of official | Same word of official (vs. unofficial) |
| Same word of officialize, officialise | Same word of officiate | Same word of offish |
| Same word of offload | Same word of offsaddle | Same word of offset |
| Same word of offset, set off | Same word of offshore | Same word of offstage |
| Same word of ogle | Same word of oil | Same word of oil-bearing |
| Same word of oil-fired | Same word of oily | Same word of oily, oleaginous |
| Same word of oily,oleaginous | Same word of old | Same word of old (vs. new) |
| Same word of old (vs. young) | Same word of old(prenominal) | Same word of old(prenominal), |
| Same word of old, older | Same word of old, onetime(prenominal), one-time(prenominal), quondam(prenominal), sometime(prenominal | Same word of old-fashioned, old-hat(predicate |
| Same word of old-hat | Same word of old-maidish, old-womanish | Same word of old-time, quaint, olde worlde |
| Same word of old-world | Same word of olden | Same word of older |
| Same word of oldish | Same word of oldline, old-line | Same word of oleophilic (vs. oleophobic) |
| Same word of olive | Same word of olive-brown | Same word of olive-colored, olive-coloured |
| Same word of olive-drab | Same word of olive-grey, olive-gray | Same word of olivelike, olive-like |
| Same word of olympian | Same word of omen | Same word of ominous |
| Same word of omissible | Same word of omit | Same word of omnibus(prenominal) |
| Same word of omnifarious | Same word of omnipotent | Same word of omnipresent |
| Same word of omniscient | Same word of omnivorous (vs. insectivorous) (vs. carnivorous) (vs. herbivorous) | Same word of on (vs. off) |
| Same word of on fire(predicate) | Same word of on guard, on one's guard(predicate), upon one's guard(predicate), on your guard | Same word of on hand(predicate) |
| Same word of on tap(predicate) | Same word of on the fence(predicate) | Same word of on the go(predicate) |
| Same word of on the hook(predicate) | Same word of on the job(predicate | Same word of on the loose(predicate) |
| Same word of on the nose, on the button | Same word of on the offensive(predicate) | Same word of on the table |
| Same word of on trial | Same word of on-key | Same word of on-line (vs. off-line), online |
| Same word of on-line(prenominal), online | Same word of on-site (vs. off-site) | Same word of on-the-spot(prenominal), on-the-scene(prenominal) |
| Same word of oncoming | Same word of one | Same word of one hundred |
| Same word of one hundred fifteen | Same word of one hundred fifty | Same word of one hundred fifty-five |
| Same word of one hundred five, | Same word of one hundred forty, | Same word of one hundred forty-five |
| Same word of one hundred ninety | Same word of one hundred one | Same word of one hundred seventy |
| Same word of one hundred seventy-five | Same word of one hundred sixty | Same word of one hundred sixty-five |
| Same word of one hundred ten, | Same word of one hundred thirty | Same word of one hundred thirty-five |
| Same word of one hundred twenty | Same word of one hundred twenty-five | Same word of one thousand |
| Same word of one(prenominal) | Same word of one(prenominal), one and only(prenominal) | Same word of one, 1, i, ane |
| Same word of one-armed | Same word of one-celled | Same word of one-dimensional |
| Same word of one-eared | Same word of one-eyed | Same word of one-handed |
| Same word of one-horse | Same word of one-man(prenominal), one-person(prenominal), one-woman(prenominal) | Same word of one-member |
| Same word of one-on-one | Same word of one-on-one, man-to-man | Same word of one-party |
| Same word of one-seeded, one-seed | Same word of one-sided | Same word of one-step |
| Same word of one-to-one | Same word of one-way | Same word of one-winged |
| Same word of one-year-old | Same word of ongoing, on-going | Same word of only |
| Same word of onshore | Same word of ooh | Same word of ooze |
| Same word of ooze out, ooze | Same word of ooze through | Same word of oozing, oozy |
| Same word of opacify | Same word of opalesce | Same word of opalescent, opaline |
| Same word of opalize, opalise | Same word of opaque | Same word of opaque (vs. clear) |
| Same word of open | Same word of open (vs. closed) | Same word of open (vs. closed), opened |
| Same word of open (vs. shut), unfastened | Same word of open fire | Same word of open up |
| Same word of open(prenominal) | Same word of open, open up | Same word of open, opened |
| Same word of open-air(prenominal) | Same word of open-and-shut | Same word of open-chain |
| Same word of open-collared | Same word of open-ended | Same word of open-minded |
| Same word of open-plan | Same word of opencast, opencut | Same word of openhanded |
| Same word of openhearted | Same word of opening (vs. closing) | Same word of openmouthed |
| Same word of operable, operational | Same word of operable, practicable | Same word of operate |
| Same word of operate on, operate | Same word of operate, control | Same word of operate, run |
| Same word of operational (vs. nonoperational) | Same word of operational, in operation(predicate), operating(prenominal) | Same word of operative |
| Same word of operative (vs. inoperative) | Same word of operose | Same word of opine |
| Same word of opinionated, opinionative, self-opinionated | Same word of opisthognathous (vs. prognathous) | Same word of opponent, opposing |
| Same word of opportune (vs. inopportune) | Same word of opportunist, opportunistic | Same word of oppose |
| Same word of opposed (vs. unopposed) | Same word of opposite | Same word of oppositive |
| Same word of oppress | Same word of oppressed | Same word of oppressive |
| Same word of opprobrious | Same word of oppugn | Same word of opsonize |
| Same word of opt out | Same word of optimistic | Same word of optimistic (vs. pessimistic) |
| Same word of optimize, optimise | Same word of optimize, optimise | Same word of optimum, optimal |
| Same word of optional (vs. obligatory) | Same word of opulent | Same word of oracular |
| Same word of oral | Same word of oral (vs. aboral) | Same word of orange, orangish |
| Same word of orange-brown | Same word of orange-colored, orange-coloured, orange-hued | Same word of orange-flowered |
| Same word of orange-red, orangish-red | Same word of orange-sized | Same word of orate |
| Same word of oratorical | Same word of orb, orbit, | Same word of orbicular |
| Same word of orbiculate, orbicular | Same word of orbitual | Same word of orchestrate |
| Same word of ordain | Same word of ordain,ordinate, order | Same word of order |
| Same word of ordered | Same word of ordered (vs. disordered) | Same word of orderly |
| Same word of ordinal (vs. cardinal) | Same word of ordinary | Same word of ordinary (vs. extraordinary) |
| Same word of ordinate | Same word of organic | Same word of organic (vs. inorganic) |
| Same word of organize, organise | Same word of organize, organise, orchestrate | Same word of organized (vs. disorganized) |
| Same word of organized (vs. unorganized) | Same word of organized, organised, | Same word of orgiastic |
| Same word of orient | Same word of orient, orientate | Same word of oriental |
| Same word of orientalize, orientalise | Same word of oriented (vs. unoriented), orientated | Same word of orienting (vs. disorienting), orientating |
| Same word of original | Same word of original | Same word of original (vs. unoriginal) |
| Same word of originate | Same word of originative | Same word of ornament |
| Same word of ornamental | Same word of ornate | Same word of ornery |
| Same word of orotund | Same word of orphan | Same word of orphaned |
| Same word of orthodox (vs. unorthodox) | Same word of orthogonal | Same word of orthomolecular |
| Same word of orthostatic | Same word of Oscan-speaking | Same word of oscillate |
| Same word of oscillate, vibrate | Same word of oscillatory, oscillating | Same word of oscitant |
| Same word of osculate | Same word of ossified | Same word of ossify |
| Same word of ostensible | Same word of ostensible, ostensive | Same word of ostensive |
| Same word of ostentate | Same word of ostentatious | Same word of ostracize, ostracise |
| Same word of otherwise | Same word of otherworldly | Same word of otiose |
| Same word of ototoxic | Same word of oval-bodied | Same word of oval-fruited |
| Same word of oval-shaped, ovate, oviform, ovoid, | Same word of ovate | Same word of oven |
| Same word of oven-ready | Same word of oven-shaped | Same word of ovenbake |
| Same word of over(predicate) | Same word of over-correct, overcompensate | Same word of over-embellished |
| Same word of over-the-counter, | Same word of over-the-counter, otc | Same word of over-the-top |
| Same word of overabundant | Same word of overachieve | Same word of overact,overplay |
| Same word of overactive | Same word of overage, overaged,over-the-hill | Same word of overall |
| Same word of overambitious | Same word of overanxious | Same word of overarch |
| Same word of overawe | Same word of overawed | Same word of overbalance |
| Same word of overbear | Same word of overbearing | Same word of overbid |
| Same word of overblown | Same word of overboil | Same word of overbold |
| Same word of overburden | Same word of overburdened | Same word of overbusy |
| Same word of overcapitalize, overcapitalise | Same word of overcareful | Same word of overcast |
| Same word of overcautious | Same word of overcharge | Same word of overcloud |
| Same word of overcome | Same word of overcompensate | Same word of overconfident |
| Same word of overcook | Same word of overcredulous | Same word of overcritical |
| Same word of overcrop, overcultivate | Same word of overcrowd | Same word of overcurious |
| Same word of overdelicate | Same word of overdo | Same word of overdone |
| Same word of overdone, overstated | Same word of overdose | Same word of overdramatize, overdramatise |
| Same word of overdraw | Same word of overdress | Same word of overdress, overclothe |
| Same word of overdressed | Same word of overdrive | Same word of overdue |
| Same word of overeager | Same word of overemotional | Same word of overemphasize, overemphasise, overstress |
| Same word of overenthusiastic | Same word of overestimate, overrate | Same word of overexcited |
| Same word of overexert | Same word of overexploit | Same word of overexpose |
| Same word of overfamiliar | Same word of overfed | Same word of overfeed |
| Same word of overfill | Same word of overflow | Same word of overflow, overrun |
| Same word of overflowing | Same word of overfly | Same word of overfond |
| Same word of overfull | Same word of overgeneralize, overgeneralise | Same word of overgreedy |
| Same word of overgrow | Same word of overgrown | Same word of overhand (vs. underhand), overhanded, overarm |
| Same word of overhand, oversewn | Same word of overhang | Same word of overhasty |
| Same word of overhaul, | Same word of overhear | Same word of overheat |
| Same word of overheated | Same word of overindulge,overgorge, overeat | Same word of overindulgent |
| Same word of overjealous | Same word of overjoy | Same word of overjoyed |
| Same word of overladen, overloaded | Same word of overland | Same word of overlap |
| Same word of overlarge | Same word of overleap | Same word of overlie |
| Same word of overlie, overlay | Same word of overload | Same word of overload,overcharge |
| Same word of overlook | Same word of overlook, overtop | Same word of overlooked |
| Same word of overlooking | Same word of overlying | Same word of overmodest |
| Same word of overmuch | Same word of overnice | Same word of overnight |
| Same word of overpay | Same word of overplay,overact | Same word of overpopulate |
| Same word of overpower, overmaster, overwhelm | Same word of overpowering, overwhelming | Same word of overpraise |
| Same word of overprice | Same word of overpriced | Same word of overprint |
| Same word of overproduce | Same word of overprotect | Same word of overprotective |
| Same word of overproud | Same word of overreach | Same word of overreaching |
| Same word of overreact | Same word of overrefine, over-refine | Same word of overrefined |
| Same word of override | Same word of overriding | Same word of overripe |
| Same word of overrule, overturn, override, overthrow | Same word of overrun | Same word of oversea |
| Same word of overseas | Same word of oversee | Same word of oversensitive |
| Same word of overserious | Same word of oversew | Same word of oversexed |
| Same word of overshadow | Same word of overshoot | Same word of overshot |
| Same word of oversimplify | Same word of oversize, oversized | Same word of oversolicitous |
| Same word of overspecialize, overspecialise | Same word of overspend | Same word of overspread |
| Same word of overstate | Same word of overstate,overdraw | Same word of overstay, outstay |
| Same word of overstep | Same word of overstock | Same word of overstrain, overextend |
| Same word of overstretch | Same word of overstrung | Same word of overstuff |
| Same word of overstuffed | Same word of oversubscribed | Same word of oversupply |
| Same word of oversuspicious | Same word of overt (vs. covert), open | Same word of overtake, overhaul |
| Same word of overtax | Same word of overthrow,overturn | Same word of overtire, overweary, overfatigue |
| Same word of overtrump | Same word of overturn | Same word of overturned |
| Same word of overuse, overdrive | Same word of overvaliant | Same word of overvalue, overestimate |
| Same word of overweening | Same word of overweight | Same word of overwhelm |
| Same word of overwhelm, overpower,overcome, overtake | Same word of overwhelming | Same word of overwinter |
| Same word of overwork | Same word of overwork, | Same word of overwrite |
| Same word of overwrought | Same word of overzealous | Same word of oviparous (vs. ovoviviparous) (vs. viviparous) |
| Same word of ovulate | Same word of owe | Same word of owing(predicate), |
| Same word of owlish | Same word of own up | Same word of own(prenominal) |
| Same word of owned (vs. unowned) | Same word of owner-occupied | Same word of ox-eyed |
| Same word of oxford-grey, oxford-gray | Same word of oxidative | Same word of oxidise, oxidize, oxidate |
| Same word of oxidizable | Same word of oxidize, oxidise, oxidate | Same word of oxidized, oxidised |
| Same word of oxygenate, oxygenize, oxygenise, | Same word of oxygenize, oxygenise | Same word of oyster |
| Same word of ozonize, ozonise |
