"What is the plural of the word 'zero'? I'd always understood that it was 'zeros' not 'zeroes', but I'm starting to see both forms crop up with increasing regularity. Is this a US English/UK English difference or just errors?
"If it is zeros, why do we then refer to heroes and not heros? (Could be worse I suppose, at least I've never seen anyone write hero's... yet). Don't both words have Greek origins?"
My first instinct was 'zeros', and this was confirmed by my Concise OED, which doesn't give 'zeroes' at all. However Webster's and the American Heritage Dictionary give equal weight to both variants, suggesting it is a difference between British and American English.
As for the etymology of the words, hero is indeed from Greek, whereas zero comes from the Arabic 'sifr', which means 'zero' or 'nothing'. It also gave us the English word 'cipher'. So 'hero' and 'zero' have different etymologies as well as different plural forms.
So why are both 'zeros' and 'zeroes' in use Stateside? I'm not sure, but it could well be out of association with 'heroes' and similar '-oes' plurals. Not that all nouns ending in 'o' take 'oes' in the plural; some take just 's' (logo – logos), and others can happily go either way according to the OED (mango – mangos or mangoes).
Put it down as just another irregularity in English spelling – albeit one that may disappear over time, as the increasing use of 'zeroes' suggests is already happening.