Index - O
| objectName | Interlude |
| ObjectWithSingleField | Interlude |
| odd | Interlude |
| omitNothingFields | Interlude |
| on | Interlude |
| OnDecodeError | Interlude |
| one | Interlude |
| OnError | Interlude |
| onException | Interlude |
| openFile | Interlude |
| OpenPunctuation | Interlude |
| Option | |
| 1 (Data Constructor) | Interlude |
| 2 (Type/Class) | Interlude |
| option | Interlude |
| optional | Interlude |
| Options | Interlude |
| or | Interlude |
| orAlt | Interlude |
| Ord | Interlude |
| ord | Interlude |
| Ordering | Interlude |
| ordNub | Interlude |
| ordNubOf | Interlude |
| orElse | Interlude |
| orEmpty | Interlude |
| OtherLetter | Interlude |
| OtherNumber | Interlude |
| OtherPunctuation | Interlude |
| OtherSymbol | Interlude |
| otherwise | Interlude |
| Overflow | Interlude |
| overflowError | Interlude |