The /ɔ/ vowel is usually spelled <or>, <our>, and <oar>, but we also see <al> in tall, <au> in caught, and <aw> in awl. The /ɔɪ/ diphthong is spelled <oi> or <oy>.
This is a contrast between a long vowel and a diphthong. The starting positions are close togther in the mouth and there is some potential for confusion, though not associated with any particular group of learners. For speakers of French, which uses a clear -l after vowels, there might be a tendency to confuse pairs like call/coil.
Interesting pairs include:
The density figure is high at 11.9%. The set makes 47 semantic contrasts giving a loading of 51%.
all oil awl oil awls oils bald boiled ball boil balling boiling balls boils bawd buoyed boar boy boars boys boar buoy boars buoys bore boy bores boys bore buoy bores buoys bored buoyed brawl broil brawled broiled brawling broiling brawls broils brawler broiler brawlers broilers call coil called coiled calling coiling calls coils caught quoit caw coy Claud cloyed clause cloys claw cloy clawing cloying clawed cloyed claws cloys corn coign corns coigns corn coin corned coined corning coining corns coins corner coiner corners coiners court quoit courts quoits Dawley doily deplore deploy deplored deployed deplores deploys fall foil falling foiling falls foils faugh Fowey for Fowey fore Fowey forced foist gnaws noise implore employ implored employed implores employs jaunt joint jaunted jointed jaunting jointing jaunts joints jaw joy jawed joyed jawing joying jaws joys lauds Lloyd's lawn loin lawns loins lords Lloyd's maul moil mauled moiled mauling moiling mauls moils pause poise paused poised pauses poises pausing poising raw Roy recall recoil recalled recoiled recalling recoiling recalls recoils saw soy soar soy sore soy tall toil taller toiler tor toy tors toys tore toy
Credit: John Higgins