| He doesn't think that | No cree que |
| I don't think that | No creo que |
| I doubt that | Dudo que |
| It's not certain that | No es cierto que |
| It's not sure that | No es seguro que |
| It's not true that | No es verdad que |
| Maybe | Tal vez |
| Perhaps | Quizás |
| They don't think that | No creen que |
| We don't think that | No creemos que |
| We doubt that | Dudamos que |
| You all doubt that | Dudan que |
| You doubt that | Dudas que |