| necessary(clear, sound, reasonable, sensible, rational) |
| normal(conventional, customary, established) |
| objective(adjective, correct, honest, fair, proper) |
| obvious(clear, sound, reasonable, sensible, rational) |
| of right(expression, adjective, proper, legitimate, lawful) |
| off-Broadway |
| okay(adjective, good, right, reasonable, fit) |
| okayed(conventional, customary, established, allowed, exempt) |
| on the button(expression, idiom, sharp, appropriate, suitable) |
| on the line(expression, idiom, open, direct, right) |
| on the nose(expression, idiom, sharp, appropriate, suitable) |
| on the up(expression, idiom, deliberate, witting, valid) |
| on up and up(expression, idiom, certain, deliberate, true) |
| opportune(good, fit, appropriate, acceptable, related) |
| ordered(adjective, lawful) |
| original(good, sound, right, reasonable, pure) |
| orthodox(correct, fair, proper, conventional, customary) |
| pardonable(adjective, reasonable, justified, defensible) |
| passed(adjective, proper, just, legitimate, lawful) |
| penetrating(sharp, critical, meaningful, incisive, biting) |