The /ɒ/ vowel is spelled <o>, or <a> after <w> in was and wand. The /aʊ/ diphthong is spelled <ow> or <ou>.
This contrast is between a short vowel and a diphthong. The starting position of the tongue in the mouth is fairly close. It has been reported as a problem for Farsi and Vietnamese speakers, but it is not a widespread source of confusion.
Interesting pairs include:
The density value is 4.68%. The pairs make 50 semantic contrasts, giving a loading of 50%.
bond bound bonded bounded bonding bounding bonds bounds bronze browns clod cloud clods clouds clot clout clots clouts clotted clouted clotting clouting cod cowed col cowl cols cowls consul council consuls councils cont count continence countenance corrie cowrie corries cowries crotch crouch crotches crouches don down donned downed donning downing dons downs doss douse dossed doused dossing dousing dosses douses dosser dowser dossers dowsers dot doubt dots doubts dotted doubted dotting doubting dotty doughty folly foully fond found fonder founder fondling foundling font fount fonts founts frond frowned frosty frowsty got gout holler howler hollers howlers jolly jowly jollier jowlier jolliest jowliest knot knout knots knouts loss louse lot lout lots louts moss mouse mosses mouses mossy mousy mossier mousier mossiest mousiest moth mouth moths mouths otter outer plod ploughed ponce pounce ponces pounces pond pound ponds pounds ponder pounder ponders pounders pot pout potted pouted potting pouting pots pouts prod proud rod rowed rondel roundel rondels roundels rot rout rots routs rotted routed rotting routing Scot scout Scots scouts shot shout shots shouts snot snout spot spout spots spouts spotted spouted spotting spouting tot tout tots touts totted touted totting touting trot trout trots trouts wand wound was wows
Credit: John Higgins