Anyone who has read Cicero's famous line,
Quo usque tandem, Catalina, abutere patientia nostra?
...knows that the 2nd person singular passive personal ending "-ris" is often changed to "-re":
- laudaris > laudare
- hortaberis > hortabere
- mittaris > mittare
- audireris > audirere
Some of these--especially "mittare"--sound pretty strange to me. Others seem natural.
I have two related questions:
- Are there rules or guidelines, beyond obvious metrical constraints, about when to use either form?
- Do we have information about the relative frequency of -ris vs. -re?