The /ɔ/ vowel is usually spelled <or> and <oar>, but we also see <a> in ball and hall, <au>, <aw> and <ar> after <w> in warned. The /u/ vowel is spelled <oo>, <u> or <ew>, and unusually <ui> in suit, <o> in womb and <ou> in the homograph wound..
This is a contrast between two long vowels. They are fairly close together in the mouth but do not seem to cause many problems for learners, except to some extent with Scandinavians who may be affected by the spelling.
Interesting pairs include:
dawdle doodle
fraught fruit
overall overrule
The density figure is 4.02%. The set makes 113 semantic contrasts giving a loading of 60.8%.
awes ooze ball buhl bawd booed boar boo boars boos boars booze board booed bore boo bored booed bores boos bores booze bought boot bourn boon broad brewed broad brood broads broods brought bruit brought brute call cool called cooled calling cooling calls cools caller cooler callers coolers caught coot cause coos caw coo cawed cooed cawing cooing caws coos chaw chew chawed chewed chawing chewing chaws chews Claud clued clause clues claw clue clawing cluing clawed clued claws clues core coo cores coos corn coon corns coons Corp coop corpse coops court coot courts coots crore crew crores crews crores cruise daw do dawdle doodle dawdled doodled dawdles doodles dawdling doodling daws do's draw drew drawl drool drawled drooled drawling drooling drawls drools fall fool falling fooling falls fools flautist flutist flautists flutists flaw flew flaws flues ford food fords foods fraught fruit Gaul ghoul Gauls ghouls gnaw gnu gnaws gnus gorse goose hall who'll haulm whom haw who hawed who'd haws who's jaw Jew jaws Jews law lieu lawn loon lawns loons law loo laws loos lord lewd Maud mood Maudie moody maw moo maws moos morn moon morns moons morning mooning Morse moose mourn moon mourned mooned mourning mooning mourns moons Norse noose overall overrule overdraw overdrew pall pool palled pooled palling pooling palls pools Paul Poole paw pooh prawn prune prawned pruned prawning pruning prawns prunes raw rue roar rue roared rued roared rood roared rude saw Sioux saw sue saws sues scald schooled shore shoe shored shooed shores shoes short chute shorts chutes short shoot shorting shooting shorts shoots shorter shooter slaw slew snored snood snores snooze snorty snooty snortier snootier snortiest snootiest soar Sioux soar sue soars sues soar sou soars sous sore Sioux sore sou sores sous sore sue sores sues sort suit sorted suited sorting suiting sorts suits sorter suitor sorters suitors spawn spoon spawned spooned spawning spooning spawns spoons stall stool stalls stools straw strew straws strews sworn swoon tall tool tor too tor two tors twos tore too tore two war woo wars woos ward wooed warm womb warms wombs warned wound wharf woof wharfs woofs withdraw withdrew wrought root yaw yew yaws yews yaw you yawed you'd yawl you'll yaws U's