The /k/ sound is spelled with <c> or <k> initially, and usually <ck> or <ke> medially or finally though we also see <c> in tic and <cc> in accord. A special case is <ch> in the RP-modified pronunciation of the loan word Reich. (Many RP speakers will use a fricative in this word.) The /f/ sound is usually spelled with <f>, <ff> or <ph>, and <gh> in cough and tough.
The contrast is between a velar stop and a labio-dental fricative, both voiceless. It causes no problems.
Taboo word pairs include cart/fart.
Interesting pairs include:
callous phallus
chorister forester
chronology phrenology
circuit surfeit
cocky coffee
coroner foreigner
klaxon flaxen
tycoon typhoon
The mean density value is 3.7%. The list makes 257 semantic distinctions, a loading of 48%.
acclaim aflame accord afford accorded afforded according affording accords affords beak beef beaks beefs buck buff bucked buffed bucks buffs bucking buffing bucket buffet bucketed buffeted bucketing buffeting buckets buffets cab fab cable fable cabled fabled cables fables cad fad cads fads caddie faddy cake fake caked faked cakes fakes caking faking calk fork calked forked calking forking calks forks call fall calling falling calls falls callous phallus callow fallow callus phallus calluses fallacies calm farm calmed farmed calming farming calms farms calmer farmer calyx califs came fame can fan canned fanned canning fanning cans fans cane feign caned feigned canes feigns caning feigning canny Fanny car far care fair cares fairs care fare cared fared cares fares caring faring carer fairer carrier farrier carriers farriers cart fart carted farted carting farting carts farts case face cased faced cases faces casing facing casings facings cast fast casts fasts casting fasting caste fast castes fasts caster faster cat fat cats fats catty fatty cattier fattier cattiest fattiest cattish fattish caught fort caught fought cause fours caw faugh caw for caw fore caw four caws fours cawed ford Celt felt chord ford chords fords chorister forester choristers foresters chronology phrenology circuit surfeit circuits surfeits clack flak clacks flax claim flame claimed flamed claiming flaming claims flames clank flank clanked flanked clanking flanking clanks flanks clan flan clans flans clap flap clapped flapped clapping flapping claps flaps clapper flapper clappers flappers Clare flair Clare flare clash flash clashed flashed clashes flashes clashing flashing clatter flatter clattered flattered clattering flattering clatters flatters Claud flawed Claud floored clause flaws clause floors claw flaw claws flaws claw floor claws floors clay flay cleat fleet cleats fleets Clem phlegm clew flew clew flue clews flues click cliff clicks cliffs click flick clicked flicked clicking flicking clicks flicks clinch flinch clinched flinched clinches flinches clinching flinching cling fling clinging flinging clings flings clip flip clipped flipped clipping flipping clips flips clipper flipper clippers flippers clock flock clocked flocked clocking flocking clocks flocks clog flog clogged flogged clogging flogging clogs flogs clone flown close floes close flows clout flout clouted flouted clouting flouting clouts flouts cluck fluff clucked fluffed clucking fluffing clucks fluffs clung flung clunk flunk clunked flunked clunking flunking clunks flunks cluster fluster clustered flustered clustering flustering clusters flusters clutter flutter cluttered fluttered cluttering fluttering clutters flutters Clwyd fluid Co foe coal foal coaled foaled coaling foaling coals foals coaming foaming coarse force coax folks cob fob cobs fobs cock cough cocked coughed cocks coughs cocking coughing cocks fox cocker coffer cockers coffers cocky coffee cog fog cogs fogs coil foil coiled foiled coiling foiling coils foils coke folk cold fold colds folds colder folder collie folly collies follies comb foam combed foamed combs foams combing foaming concur confer concurred conferred concurring conferring concurs confers cone phone coned phoned cones phones coning phoning coney phoney coneys phoneys conic phonic conned fond cont font cool fool cooled fooled cooling fooling cools fools cop fop cops fops cord ford corded forded cording fording cords fords core for cored ford cork fork corks forks corked forked corking forking corm form corms forms corn faun corns fauns corn faun corned fawned corning fawning corns fawns coroner foreigner coroners foreigners corse force corses forces corset faucet corsets faucets count fount counts founts course force coursed forced coursing forcing courses forces court fort courts forts court fought cowl foul cowling fouling cowls fouls cox fox coxed foxed coxes foxes coxing foxing coy Fowey crank frank cranked franked cranking franking cranks franks crate freight crated freighted crates freights crating freighting crater freighter craters freighters craze frays craze phrase crazed phrased crazes phrases creaky freaky creakier freakier creakiest freakiest creed freed Crieff creak crier friar criers friars cringe fringe cringed fringed cringes fringes cringing fringing crock frock crocks frocks crocked croft crossed frost crow fro crown frown crowned frowned crowning frowning crowns frowns crows froze cry fry crying frying cries fries cried fried cuddle fuddle cuddled fuddled cuddles fuddles cuddling fuddling cue few cues fuse culminate fulminate culminated fulminated culminates fulminates culminating fulminating culmination fulmination culminations fulminations cur fir curs firs cur fur curs furs curious furious curiously furiously curl furl curled furled curling furling curls furls cursed first cuss fuss cusses fusses cut phut deck deaf decked deft decker deafer dicker differ dickered differed dickering differing dickers differs dock doff docked doffed docking doffing docks doffs elk elf flux fluffs Greek grief Greeks griefs hark half harked haft incur infer incurred inferred incurring inferring incurs infers K fey K's phase kail fail karma farmer karmas farmers Kate fête keel feel keels feels keeling feeling keeled field keened fiend ken fen kens fens kenned fend kennel fennel Kerry ferry ketch fetch ketches fetches Kettering fettering kettle fettle key fee keyed feed keying feeing keys fees kicks fix kill fill kills fills killings fillings killed filled kind find kinds finds kind fined kinder finder kine fine kissed fist kit fit kits fits kitted fitted kitting fitting kite fight kites fights klaxon flaxen lakh laugh lakhs laughs lark laugh larked laughed larking laughing larks laughs leak leaf leaked leafed leaking leafing leaks leafs leaky leafy leakier leafier leakiest leafiest leek leaf licked lift like life locked loft luck luff luxe luffs muck muff mucked muffed mucks muffs muckle muffle murky murphy nick niff nicks niffs oak oaf oaks oafs Oct oft pickle piffle pickled piffled pickles piffles pickling piffling puck puff pucks puffs Q few Q's fuse queue few queues fuse queued feud quick quiff recur refer recurred referred recurring referring recurs refers reek reef reeked reefed reeking reefing reeks reefs Reich rife rick riff ricks riffs ricked riffed ricked rift ruck rough rucked roughed rucking roughing rucks roughs sake safe sakes safes sicked sift silk sylph silks sylphs snick sniff snicked sniffed snicking sniffing snicks sniffs soaker sofa soakers sofas socked soft spook spoof spooks spoofs stark staff stick stiff sticks stiffs sticker stiffer strike strife stuck stuff Styx stiffs succour suffer succoured suffered succouring suffering succours suffers suck sough sucked soughed sucking soughing sucks soughs tacky Taffy tic tiff ticks tiffs truckle truffle truckles truffles tuck tough tucks toughs tucked tuft tucker tougher Turk turf Turks turfs tycoon typhoon tycoons typhoons uncurl unfurl uncurled unfurled uncurling unfurling uncurls unfurls wake waif wakes waifs walk wharf walks wharfs wick whiff wicks whiffs wreck ref wrecks refs wrecking reffing wrecked reft X F's