The /s/ sound is spelled with <s>, <ss>, <ce> or <sw> in sword. The /r/ sound is spelled with <r>, <rr> or <wr> in write. Notice the pair sow/row and its plurals appear twice since both are homographs.
This is a contrast between a voiceless sibilant fricative and a voiced retroflex continuant. It causes no problems.
Interesting pairs include:
buxom buckram
foursome forum
fussier furrier
masonic moronic
mezzo Metro
second reckoned
senate rennet
severance reverence
suffer rougher
syllabaries syllabuses
The mean density value is 1.7%. The list makes 204 semantic distinctions, a loading of 49%.
acid arid acidity aridity assay array assayed arrayed assaying arraying assays arrays assessed arrest assize arise assizes arises Bessie berry Bessie bury buxom buckram C re calluses calories Cecil wrestle cedar reader cedars readers cede read cedes reads ceding reading ceiling reeling cent rent cents rents cider rider ciders riders cite right cited righted cites rights citing righting cite rite cites rites cite write cites writes citing writing civet rivet civets rivets classification clarification classify clarify classifying clarifying classified clarified classifies clarifies coursing coring cussed curried cusses curries cyst wrist cysts wrists decide deride decided derided decides derides deciding deriding decision derision decisive derisive decisively derisively dissect direct dissected directed dissecting directing dissects directs dissection direction dissections directions foursome forum foursomes forums fussier furrier gassy gharry gasses gharries gassy Gary horsy hoary hussy hurry hussies hurries Jessie Gerry Kassel Carol lassie Larry literacy literary losses lorries masonic moronic masses marries massy marry messy merry messier merrier messiest merriest mezzo Metro mouses Maoris mousy Maori outside outride outsides outrides oversaw overawe oversewed overrode pierces peris piercing peering primacy primary primacies primaries pursing purring reseed reread reseeding rereading reseeds rereads sack rack sacked racked sacking racking sacks racks saddle raddle saddled raddled sag rag sagged ragged sagging ragging sags rags sage rage sages rages said read said red sail rail sailed railed sailing railing sailings railings sails rails sake rake sakes rakes sale rail sales rails sally rally sallied rallied sallies rallies sallying rallying Sam ram sand rand sands rands sandy randy sandier randier sandiest randiest sane rain sane reign sane rein sang rang sank rank sap rap sapped rapped sapping rapping saps raps sapper rapper sappers rappers sap wrap sapped wrapped sapping wrapping saps wraps sapper wrapper sappers wrappers sash rash sashes rashes sat rat sate rate sated rated sates rates sating rating satyr ratter satyrs ratters saucing soaring savage ravage savaged ravaged savages ravages savaging ravaging save rave saved raved saves raves saving raving savings ravings saver raver savers ravers saw raw saw roar sawed roared saws roars say ray scent rent scented rented scenting renting scents rents scythe writhe scythed writhed scything writhing scythes writhes sea re seal real seal reel sealed reeled seals reels sealing reeling sear rear seared reared searing rearing sears rears season reason seasons reasons seasoned reasoned seasoning reasoning seasonable reasonable sec wreck secession recession secessions recessions second reckoned secs Rex secs wrecks sect wrecked sector rector sectors rectors seduce reduce seduced reduced seduces reduces seducing reducing seduction reduction seductions reductions see re seed read seeds reads seeding reading seedy reedy seedier reedier seediest reediest seek reek seeks reeks seeking reeking seethe wreathe seethed wreathed seething wreathing seethes wreathes seine rain seined rained seines rains seining raining seine rein seined reined seines reins seining reining seine reign seined reigned seines reigns seining reigning senate rennet send rend sending rending sends rends sent rent sender render senders renders sends wrens Seoul rôle Seoul roll separable reparable separation reparation separations reparations set ret sets rets setting retting severance reverence severe revere sew roe sew row sews rows sewing rowing sewed rowed sewed road sewer rower sewers rowers sewn roan sews rose sex Rex sex wrecks sick rick sicked ricked sicks ricks side ride sides rides siding riding sidings ridings sift rift sifts rifts sigh rye sighed ride sighs rise sight right sighted righted sights rights sighting righting sight rite sights rites sight write sights writes sighting writing sightings writings sign Rhine signed rind Sikh reek Sikhs reeks since rinse sing ring sings rings singing ringing sang rang sung rung sing wring sings wrings singing wringing sung wrung singer ringer singers ringers singer wringer singers wringers sink rink sinks rinks Sioux rue sire wrier sit writ sits writs site right sited righted sites rights siting righting site rite sites rites site write sites writes siting writing size rise sizes rises sizing rising so roe so row soap rope soaped roped soaps ropes soaping roping soapy ropey soapier ropier soapiest ropiest soar raw soar roar soars roars soaring roaring sob rob sobbed robbed sobs robs sobbing robbing soccer rocker sock roc sock rock socked rocked socking rocking socks rocks socket rocket sockets rockets sod rod sods rods solar roller sold rolled sole rôle soles rôles sole roll soling rolling soles rolls soled rolled some rum son run sons runs song wrong songs wrongs sonny runny soon rune sort wrought sot rot sots rots sou rue sous rues sough rough soughed roughed soughing roughing soughs roughs sought wrought soul rôle souls rôles soul roll souls rolls sound round sounded rounded sounding rounding sounds rounds soundly roundly soundness roundness sourcing soaring sow row sows rows sowing rowing sowed rowed sow row sows rows sows rouse soy Roy sub rub subbed rubbed subbing rubbing subs rubs suck ruck sucked rucked sucking rucking sucks rucks suffer rougher sum rum summer rummer sump rump sumps rumps sun run sunning running suns runs sundown rundown sunny runny sunnier runnier sunniest runniest sun-up run-up sussed rust syllabaries syllabuses unseasonable unreasonable unsold unrolled
John Higgins, Shaftesbury, November 2010.