Index - O
| odd | Mit.Prelude |
| on | Mit.Prelude |
| onException | Mit.Prelude |
| onLeftM | Mit.Prelude |
| onNothingM | Mit.Prelude |
| OpenPunctuation | Mit.Prelude |
| or | Mit.Prelude |
| Ord | Mit.Prelude |
| ord | Mit.Prelude |
| Ordering | Mit.Prelude |
| OtherLetter | Mit.Prelude |
| OtherNumber | Mit.Prelude |
| OtherPunctuation | Mit.Prelude |
| OtherSymbol | Mit.Prelude |
| otherwise | Mit.Prelude |
| Overflow | Mit.Prelude |