| Terminology | Likelihood of outcome | Equivalent terms |
| Virtually certain | >99% probability of occurrence | Almost certain |
| Very likely | >90% probability | Highly likely, very probable |
| Likely | >66% probability | Probably |
| About as likely as not | 33%-66% probability | More or less likely |
| Unlikely | <33% probability | Improbable |
| Very unlikely | <10% probability | Highly unlikely |
| Exceptionally unlikely | <1% probability |