The spelling of /p/ is either <p> or <pp>. The spelling of /s/ is more varied, including <s>, <ss>, <sc>, <c> in ceiling or <ps> in psalm.
The contrast is between a stop and a fricative, both voiceless but well separated in the mouth so that confusions are unlikely.There are several taboo word pairs but they are unlikely to cause problems: crap/crass, pee/see, and pip/piss.
Interesting pairs include
The mean density value is 2.8%. The list makes 328 semantic distinctions, a loading of 54%.
ape ace append ascend appended ascended appending ascending appends ascends appertain ascertain appertained ascertained appertaining ascertaining appertains ascertains apter aster blip bliss burped burst cape case carpal castle carpals castles carped cast carped caste cop cos coped coast copped cost Copt cost Copts costs Corp coarse Corp course crap crass creep crease creeping creasing crept crest crop cross cropped crossed cropping crossing cup cuss depend descend depended descended depending descending depends descends dependant descendant dependants descendants dope dose doped dosed doping dosing drop dross dupe deuce duped deuced epics Essex fillip Phyllis flop floss fop fosse gap gas gawp gorse grape grace grippe Greece grippe grease gripped grist grope gross groped grossed groping grossing gypped gist happed hast hip hiss hippies hisses hoped host JP JC kepis cases kip kiss kipped kissed kipping kissing kipper kisser kippers kissers lap lass leap lease leaped leased leaping leasing leaped least leapt lest leper lesser lipped list loop loose looped loosed looping loosing loopy Lucy lop loss lopped lost map mass mapped massed mapping massing mop moss moped most MP MC neap Nice neap niece OAP's oases opine assign opined assigned opines assigns opining assigning P C P's C's P sea P's seas P see P's sees pack sac packs sacs pack sack packed sacked packing sacking packs sacks pact sacked pad sad paddle saddle paddled saddled paddles saddles paddling saddling page sage pages sages pail sale pails sales pail sail pails sails pain sane pain seine pained seined paining seining pains seines paint saint painted sainted paints saints pale sail paled sailed pales sails pale sale pales sales paler sailor paling sailing palings sailings pallid sallied pally sally palm psalm palms psalms palmist psalmist palmists psalmists palter psalter palters psalters Pam Sam pane sane pane seine panes seines pang sang panned sand pans sans pap sap parky sak_e pat sat pate sate pates sates patter satyr patters satyrs pause saws pause soars pave save paved saved paves saves paving saving paw saw pawed sawed pawing sawing paws saws paw soar pawed soared paws soars paw sore paws sores pawed sword pawky Sauchie pawn sawn paxes saxes pay say paying saying PC cc pea C peas C's pea sea peas seas pea see peas sees peace cease peace peep pea-green sea-green peak seek peaking seeking peaks seeks peak Sikh peaks Sikhs peal seal pealed sealed pealing sealing peals seals pealing ceiling pealings ceilings pearly surly pearlier surlier pearliest surliest peas seize pease C's pease seas pease sees pease seize peat seat peck sec pecks secs pecked sect pedantry sedentary pediment sediment pee C pees C's pee sea pees seas pee see peeing seeing pees sees peed cede peed seed peek seek peeking seeking peeks seeks peek Sikh peeks Sikhs peel seal peeled sealed peeling sealing peels seals peeling ceiling peelings ceilings peeler sealer peelers sealers peep piece peeped pieced peeping piecing peer sear peered seared peering searing peers sears peer seer peers seers peer sere pees seize peke seek pekes seeks peke Sikh pekes Sikhs Peking seeking pelf self pence sense pending sending penned send pens sends pepped pest pepped Sept peppery pessary peptic septic per sir perceptible susceptible perceptibility susceptibility perch search perched searched perches searches perching searching perjury surgery perjuries surgeries pert cert pervade surveyed pestle Cecil pet set pets sets petting setting pet sett pets setts petal settle petaled settled petals settles Pete seat pew sue pews sues Philip Phyllis pi sigh pis sighs pick sic pick sick picked sicked picking sicking picks sicks pickle sickle pickles sickles Pict sicked pie sigh pies sighs pied sighed pied side pier sear piers sears pier seer piers seers pier sere pies size pill sill pills sills pillar Scylla pillars Scyllas pimple simple pimples simples pimply simply pin sin pinned sinned pinning sinning pins sins pinch cinch pine sign pined signed pines signs pining signing pine sine pines sines ping sing pinging singing pings sings pink sink pinker sinker pinking sinking pinks sinks pip piss pipped pissed pipping pissing pique seek piques seeks piquing seeking pique Sikh piques Sikhs pis size Pisa Caesar piston Syston piston cistern pistons cisterns pit sit pits sits pitting sitting pity city pities cities pixies sixes plain slain plait slat plaited slatted plaits slats plane slain plant slant planted slanted planting slanting plants slants plash slash plashed slashed plashes slashes plashing slashing plate slate plated slated plates slates plating slating play slay playing slaying plays slays play sleigh played sleighed playing sleighing plays sleighs player slayer players slayers pleat sleet pleated sleeted pleating sleeting pleats sleets pled sled pledge sledge pledged sledged pledges sledges pledging sledging plied slide plight sleight plighted slighted plighting slighting plights sleights plight slight plop slop plopped slopped plopping slopping plops slops plot slot plots slots plotted slotted plotting slotting plough slough ploughs sloughs plug slug plugged slugged plugging slugging plugs slugs plum slum plums slums plumb slum plumbed slummed plumbing slumming plumbs slums plummy slummy plummier slummier plummiest slummiest plump slump plumped slumped plumping slumping plumps slumps plunk slunk plush slush plushy slushy plushier slushier plushiest slushiest ply sly PM cm PO CO pock Soc pock sock pocked socked pocks socks pocket socket pockets sockets pod sod podded sodded podding sodding pods sods podium sodium poke soak poked soaked pokes soaks poking soaking poker soaker pokers soakers polar solar pole Seoul pole sole poled soled poles soles poling soling pole soul poles souls poled sold poll Sol poll sole polled soled polling soling polls soles poll Seoul poll soul polls souls polled sold pollute salute polluted saluted pollutes salutes polluting saluting pollution solution polo solo pone sewn pooh Sioux pooh sou pooh Sue Poona sooner poop soup poops soups pop sop popped sopped popping sopping pops sops pope soap popes soaps poppet posset poppets possets poppy posse poppies posses pore saw pored sawed pores saws pore soar pored soared poring soaring pores soars pore sore pores sores pored sword porn sawn port sort ported sorted porting sorting ports sorts port sought porter sorter porters sorters pose sews pose sows posse soppy post soaped pot sot pots sots pound sound pounded sounded pounding sounding pounds sounds pour saw poured sawed pours saws pour soar poured soared pouring soaring pours soars pour sore pours sores poured sword power sour powered soured powering souring powers sours prep press P's seize pub sub pubs subs puck suck pucks sucks pucker succour puckered succoured puckering succouring puckers succours pucker sucker puckers suckers puff sough puffed soughed puffing soughing puffs soughs pukka succour pukka sucker pulp pulse pulped pulsed pulping pulsing pump sump pumps sumps pun son puns sons pun sun punned sunned punning sunning puns suns punk sunk pup pus pup sup pups sups purge serge purge surge purged surged purges surges purging surging purloin sirloin purloins sirloins purport support purported supported purporting supporting purports supports purred surd purr sir purrs sirs purvey survey purveyed surveyed purveying surveying purveys surveys purveyor surveyor purveyors surveyors put soot pyre sire pyres sires pyx sicks rape race raped raced raping racing rapier racier rapist racist rapists racists repeat receipt repeated receipted repeating receipting repeats receipts ripe rice ripped wrist roped roast shipped schist sirup cirrus sloop sluice sup suss supped sussed supping sussing taped taste top toss topped tossed topping tossing toped toast tripe trice tripped tryst troop truce troupe truce VP VC wallop Wallace wept west whipped whist
John Higgins, Shaftesbury, January 2010.