Phew, I'm glad Peter Pedant is seeing sense on the pronunciation of 'omicron'; I thought his classics education had deserted him. 'Omicron' in Greek means 'short o', so the letter represents the short 'o' sound, as in 'pot', and the names of Greek letters are pronounced starting with the sounds that they represent. So 'omicron' should start 'omm' and not 'ohm'. The long 'o' sound ('oh') is represented by the letter omega which, funnily enough, means 'large (or long) o'. I wonder if those who pronounce 'omicron' as "oh-my-cron" say "omm-eh-gah" rather than "ohm-eh-gah"?