Index - O
| odd | Bio.Prelude |
| Of | Bio.Streaming, Bio.Bam |
| off | Bio.Streaming.Bgzf |
| OldDamage | Bio.Adna |
| on | Bio.Prelude |
| onError | Bio.Prelude |
| onException | Bio.Prelude |
| openBinaryFile | Bio.Prelude |
| OpenPunctuation | Bio.Prelude |
| openTwoBit | Bio.TwoBit |
| optional | Bio.Prelude |
| or | Bio.Prelude |
| Ord | Bio.Prelude |
| ord | Bio.Prelude |
| Ordering | Bio.Prelude |
| orElse | Bio.Prelude |
| OtherError | Bio.Prelude |
| OtherLetter | Bio.Prelude |
| OtherNumber | Bio.Prelude |
| OtherPunctuation | Bio.Prelude |
| OtherSymbol | Bio.Prelude |
| otherwise | Bio.Prelude |
| Overflow | Bio.Prelude |
| overlaps | Bio.Bam.Regions |