The /s/ sound is spelled with <s>, <ss> or <c>. The /ʧ/ sound is spelled with <ch>, <tch> or <cz> in Czech.
This is a contrast between a sibilant fricative and an alveolar affricate, fairly close together in the mouth and both voiceless. In spite of the similarity it does not seem to cause problems.
Taboo word pairs include arse/arch and piss/pitch.
Interesting pairs include:
The mean density value is 1.4%. The list makes 108 semantic distinctions, a loading of 49%.
ace H aces H's arse arch arses arches bass batch beast beached boss botch bossed botched bosses botches bossing botching burst birched civvies chivies coast coached cons conch cross crotch crosses crotches C's cheese denser denture grouse grouch groused grouched grouses grouches grousing grouching hast hatched hiss hitch hissed hitched hisses hitches hissing hitching Horace Horwich hussies hutches insane enchain Inst inched kiss kitsch lass latch lasses latches lease leach leased leached leases leaches leasing leaching lease leech leases leeches lesser lecher mass match massed matched masses matches massing matching mast marched moose mooch mooses mooches muss much Norse nautch pass parch passed parched passes parches passing parching peace peach piece peach pieced peached pieces peaches piecing peaching piss pitch pissed pitched pisses pitches pissing pitching post poached priest preached psalm charm psalms charms purse perch pursed perched purses perches pursing perching puss putsch pussies putsches rest retched S etch S's etches sad Chad safe chafe safes chafes sane chain sap chap sapped chapped sapping chapping saps chaps sat chat satyr chatter satyrs chatters Sauchie chalky saw chaw sawed chawed sawing chawing saws chaws saw chore saws chores sear cheer seared cheered searing cheering sears cheers search church searches churches seas cheese seat cheat seated cheated seating cheating seats cheats sec check secs checks sec cheque secs cheques sec Czech secs Czechs sect checked seek cheek seeks cheeks seeking cheeking sees cheese seine chain seined chained seines chains seining chaining seize cheese seizes cheeses Selsey Chelsea sensory century sews chose sex Czechs sickle chicle sick chick sicks chicks side chide sided chided sides chides sighed chide sign chine signs chines Sikh cheek Sikhs cheeks silly chilly sillier chillier silliest chilliest silly chilli sillies chillies silly Chile since cinch sink chink sinking chinking sinks chinks Sioux chew sirup chirrup sirups chirrups sizzle chisel sizzled chiselled sizzles chisels sizzling chiselling soak choke soaked choked soaking choking soaks chokes soaker choker soakers chokers soar chaw soars chaws soar chore soars chores Soc choc sock choc socked chocked socking chocking socks chocks some chum sop chop sopped chopped sopping chopping sops chops soppy choppy soppier choppier soppiest choppiest sore chaw sores chaws sore chore sores chores sorely Chorley sou chew sous chews sow chow sows chows sows chose stress stretch stressed stretched stresses stretches stressing stretching succour chukker succours chukkers suck chuck sucked chucked sucking chucking sucks chucks sucker chukker suckers chukkers suckle chuckle suckled chuckled suckles chuckles suckling chuckling sum chum summed chummed summing chumming sums chums sump chump sumps chumps sunk chunk suss such Swiss switch tense tench twist twitched whence wench wince winch winced winched winces winches wincing winching
John Higgins, Shaftesbury, November 2010.