The /u/ vowel is usually spelled <oo>, <u>, <o> after <w> in womb and who, and occurs in the letter name U. The /3/ vowel is spelled <ur>, <ir>, <er> and <or> after <w> in worm. The two sounds together form the expression of surprise associated with schoolboy fiction and with the comedian Frankie Howerd, "Oo-er!"
This is a contrast between two long vowels, fairly close in the mouth but distinguished by lip-rounding. It is not a problem for any group of learners.
Interesting pairs include:
The density figure is 2.76%. The set makes 41 semantic contrasts giving a loading of 48.2%.
blue blur blued blurred blues blurs boo burr boos burrs booed bird boon burn boons burns boost burst boosting bursting boosts bursts booty Bertie booze burrs chute shirt chutes shirts cooed curd cool curl cooled curled cooling curling cools curls cooler curler coolers curlers coolie curly coo cur coos curs coot curt flute flirt fluted flirted flutes flirts fluting flirting fool furl fooled furled fooling furling fools furls ghoul girl ghouls girls ghoulish girlish hoot hurt hooting hurting loon learn loons learns Luke lurk lunar learner mooses mercies noose nurse noosed nursed nooses nurses noosing nursing ooze errs pool pearl pooled pearled pooling pearling pools pearls school skirl schools skirls scoot skirt scooted skirted scooting skirting scoots skirts shoot shirt shooting shirting shoots shirts slew slur slewed slurred slews slurs sou sir sous sirs spoon spurn spooned spurned spooning spurning spoons spurns suture searcher sutures searchers tootle turtle tootles turtles U's years who'd heard who'll hurl who's hers womb worm wombs worms woo were woo whirr wooed whirred woos whirrs
John Higgins, Shaftesbury, December 2009