The spelling of /k/ is <c>, <ck>, <ch> or <k>. The /ʧ/ sound is spelled <ch>, <tch> or <tsch> in bortsch.
This is a contrast between a stop and an affricate, both voiceless but fairly well separated in the mouth. It does not cause many problems.
Interesting pairs include:
caisson chasten
captor chapter
coax chokes
nacre nature
The figure for the mean density is 2.1%. The set makes 122 semantic contrasts, a loading of 52%.
ache H arc arch attack attach attacked attached attacking attaching back batch balk bortsch beak beach beaked beached bleak bleach bloc blotch block blotch book butch broke broach burke birch burked birched burking birching cad Chad caisson chasten caissons chastens calf chaff Cali Charlie calk chalk calked chalked calking chalking calks chalks calm charm calmed charmed calming charming calms charms calmer charmer camp champ camped champed camping champing camps champs campion champion cane chain caned chained canes chains caning chaining can't chant cap chap capped chapped capping chapping caps chaps captor chapter captors chapters car char cars chars card chard cards chards care chair cared chaired cares chairs caring chairing cart chart carted charted carting charting carts charts carter charter carters charters case chase cased chased cases chases casing chasing cat chat cats chats cattle chattel catty chatty cattier chattier cattiest chattiest cause chaws cause chores caw chaw cawed chawed cawing chawing caws chaws caw chore caws chores cluck clutch clucked clutched clucking clutching coax chokes cock choc cocked chocked cocking chocking cocks chocks coke coach coked coached coking coaching come chum comes chums coming chumming coo chew cooed chewed cooing chewing coos chews cop chop copping chopping cops chops copped chopped copier choppier copper chopper coppers choppers Copt chopped copy choppy copyist choppiest core chaw cored chawed coring chawing cores chaws core chore cores chores cork chalk corks chalks corked chalked corking chalking cow chow cows chows Cowes chows crock crotch curl churl curls churls Dacca dacha Dick ditch dickeys ditches duck Dutch ducky duchy duckies duchies eke each hack hatch hacked hatched hacking hatching hick hitch karma charmer karmas charmers keeper cheaper Kerry cherry keys cheese kick chick kicks chicks kick kitsch kine chine kink chink kinked chinked kinking chinking kinks chinks kip chip kipped chipped kit chit kits chits knock notch knocked notched knocking notching lack latch lacked latched lacking latching lackeys latches lakh larch leak leach leaked leached leaking leaching leak leech leek leach lurk lurch lurked lurched lurking lurching mac match mark march marked marched marking marching marker marcher markers marchers milk milch muck much mulct mulched nacre nature Nick niche pack patch packed patched packing patching park parch parked parched parking parching peak peach peaked peached peaking peaching perk perch perked perched perking perching picker pitcher pickers pitchers poke poach poked poached poking poaching poker poacher pokers poachers pork porch quays cheese rack ratch racket ratchet rackets ratchets recces retches reek reach reeked reached reeking reaching rick rich smirk smirch smirked smirched smirking smirching snack snatch snacked snatched snacking snatching snick snitch snicked snitched snicking snitching speak speech stark starch stick stitch sticking stitching suck such talk torch talker torture talkers tortures talkies torches teak teach tuck touch tucked touched tucking touching untucked untouched wick which wick witch wreck retch wrecked retched wrecking retching wreck wretch