Often—ŏf´n, not ŏf´tĕn.
Omega—o-mē´ga or o-mĕg´a, not ŏm´e-ga. Worcester allows the first only.
Onerous—ŏn´er-ous, not ō´ner-oŭs.
Only—ōn´ly, not ŭn´ly.
Onyx—ō´nyx, not ŏn´yx.
Opal—ō´-pal, not ō-păl´ nor ō-pawl´.
Opponent—op-pō´nent, not ŏp´po-nent.
Ordnance, not ordinance, when cannon, artillery, etc., are intended. Ordinance is a rule established by authority.
Orgeat—ôr´zhat or ôr´zhā, not ôr´je-at. Worcester gives ôr´zhat.
Orthoepy—ôr´tho-e-py, not ôr-thō´e-py.