The /f/ sound is spelled with <f> or <ff>, and exceptionally <gh> in laughed. The /s/ sound is spelled <s>, <ss>, <c>, or exceptionally <sc> in muscle and <ps> in psalm.
The contrast is between a labio-dental fricative and a palato-alveolar fricative, both voiceless. Most languages operate with similar sounds as phonemes, so they are not usually a problem.
Taboo word pairs include fuck/suck and its inflections.Interesting pairs include:
buffoon bassoon
diffidence dissidence
fallacious salacious
fatter satyr
fecund second
feeling ceiling
fervent servant
fickle sickle
infuse ensues
offend ascend
suffix Sussex
The mean density value is 2.3%. The list makes 222 semantic distinctions, a loading of 51%.
beefed beast buff bus buffed bused buffing busing buffoon bassoon buffoons bassoons chafe chase chafed chased chafing chasing confession concession confessions concessions confine consign confined consigned confines consigns confining consigning confinement consignment confinements consignments confirmation consummation confirmations consummations cough cos coughed cost countrified countryside Crieff crease croft crossed cuff cuss defeat deceit defeats deceits defecate dessicate defecates dessicates defecated dessicated defect dissect defected dissected defecting dissecting defects dissects defection dissection defections dissections defend descend defended descended defending descending defends descends defendant descendant defendants descendants defied decide diffidence dissidence diffident dissident doff doss doffed dossed doffing dossing elf else F S fable sable fables sables fact sacked fad sad fag sag fagged sagged fagging sagging fags sags fail sail failed sailed failing sailing failings sailings fails sails fail sale fails sales fain sane fain seine faint saint fainted sainted faints saints faintly saintly fake sake fakes sakes fallacious salacious fallow sallow falter psalter falters psalters fame same fang sang fanned sand fans sans farm psalm farms psalms fat sat fate sate fates sates fatter satyr faucet forfeit faucets forfeits faugh saw faugh sore fault salt faulted salted faulting salting faults salts faulty salty faultier saltier faultiest saltiest faun sawn fawn sawn favour saver favours savers favour savour favoured savoured favouring savouring favours savours Fawley sorely fear sear feared seared fearing searing fears sears fecund second Fed said fee C fees C's fee see feeing seeing fees sees feed cede feeds cedes feeding ceding feed seed feeds seeds feeding seeding feeder cedar feeders cedars feeler sealer feelers sealers feeling ceiling feelings ceilings feet seat feign sane feign seine feigned seined feigning seining feigns seines felicitation solicitation felicitations solicitations felicitous solicitous felicitously solicitously fell cell fells cells fell sell felling selling fells sells fence sense fenced sensed fences senses fencing sensing fencer censer fencers censers fend send fending sending fends sends fender sender fenders senders fens sends ferried serried fervent servant fervour server fête sate fêted sated fêting sating fêtes sates fetter setter fetters setters fettle settle feud pseud feuds pseuds few sue fewer sewer fey say fez says fickle sickle fie sigh fiesta siesta fiestas siestas fight cite fighting citing fights cites fight sight fighting sighting fights sights fight site fights sites filly silly fillies sillies finch cinch find signed fine sign fines signs fining signing fined signed finical cynical fir sir firs sirs fire sire fired sired fires sires firing siring fist cyst fists cysts fit sit fits sits fitting sitting fittings sittings fitter sitter fitters sitters fix sicks fix six fixes sixes fizzle sizzle fizzled sizzled fizzles sizzles fizzling sizzling flag slag flags sags flak slack flake slake flaked slaked flakes slakes flaking slaking flap slap flapped slapped flapping slapping flaps slaps flash slash flashed slashed flashes slashes flashing slashing flat slat flats slats flaw slaw flax slacks flay slay flaying slaying flays slays flay sleigh flayed sleighed flays sleighs fled sled fledge sledge fledged sledged fledges sledges flew slew flicker slicker flickers slickers flier slyer flight sleight flights sleights flight slight flighted slighted flighting slighting flights slights fling sling flinging slinging flings slings flip slip flipped slipped flips slips flipping slipping floe sloe floes sloes flow slow flows slows flowing slowing flowed slowed flog slog flogged slogged flogging slogging flogs slogs flop slop flopped slopped flops slops flopping slopping floppy sloppy floppier sloppier floppiest sloppiest flue slew flues slews fluff slough fluffed sloughed fluffing sloughing fluffs sloughs flung slung flunk slunk flurry slurry flush slush fly sly foal Seoul foal sole foaling soling foals soles foaled soled foal soul foaled sold fob sob fobbed sobbed fobbing sobbing fobs sobs foe sew foes sews foe so foe sow foes sows foggy soggy foggier soggier foggiest soggiest foil soil foiled soiled foiling soiling foils soils folk soak folks soaks Foochow Soochow foot soot footed sooted footing sooting fop sop fops sops for saw for soar fore saw fore soar four saw fours saws four soar fours soars force sauce forced sauced forces sauces forcing saucing ford sawed found sound founded sounded founding sounding founds sounds Fowey soy fox socks fuck suck fucked sucked fucking sucking fucks sucks fucker sucker fuckers suckers fucker succour fuckers succours fun son fun sun fund sunned funk sunk funny sonny funny sunny funnier sunnier funniest sunniest funnily sunnily fuse sues fuss suss fusses susses fussing sussing fussed sussed gaff gas Geoff Jess goof goose graft grassed graph grass grief grease huffy hussy humph humps infuse ensues knife nice laughed last leaf lease leafed leased leafing leasing left lest life lice lift list lifted listed lifting listing lifts lists loft lost luffed lust muff muss muffed mussed muffing mussing muffle muscle muffled muscled muffles muscles muffling muscling mufti musty murphy mercy murphies mercies offend ascend offended ascended offending ascending offends ascends phaeton Satan phaetons Satans phone sewn phonic sonic profess process professed processed professes processes professing processing profession procession professions processions puff pus reft rest relief release rife rice rift wrist rifts wrists roofed roost roughed rust ruffle rustle ruffled rustled ruffles rustles ruffling rustling shift schist shifts schists sifter sister sifters sisters sough suss soughed sussed soughing sussing suffix Sussex toff toss toffees tosses turf terse unfold unsold weft west