The schwa has many spellings. The /əʊ/ diphthong is spelled <oCe>, <o>, <ow>, and <eau> in rondeau, and occurs in the letter name O.
This is a contrast between a short vowel which is always unstressed and a diphthong. It is not in itself a problem for learners.
Interesting pairs include:
The density figure is 1.04%. The set makes 39 semantic contrasts giving a loading of 58.2%.
a O Allah aloe avert overt Bella bellow borough burrow boroughs burrows Calor callow canter canto canters cantos commander commando commanders commandoes 'em ohm fellah fellow feller fellow fellers fellows ferment foment fermented fomented fermenting fomenting ferments foments hearer hero hearers heroes h'm home h'mming homing h'ms homes holler hollow hollered hollowed hollers holloas lager largo lagers largos leader lido leaders lidos limber limbo limbers limbos linger lingo lingers lingoes marina merino marinas merinos oriel aureole oriels aureoles pillar pillow pillared pillowed pillars pillows platter plateau platters plateaus quarter quarto quarters quartos rector recto rectors rectos Rhondda rondeau romance Romance salad sallowed salver salvo salvers salvoes silicon silicone temper tempo tempers tempos the tho' to toe to tow toga Togo 'un own vacation vocation vacations vocations wallah wallow wallahs wallows winner winnow winners winnows
John Higgins, Shaftesbury, December 2009