Before a ris(re) ending what happens
the i changes to e for all 3rd groups present
Imperfect
Bar, baris/bare, bamur, bamini, bantur
Future
1st/2nd: bor, beris/bere, bitur, bimur, bimini, buntur
3rd/4th: ar, eris/ere, etur, emur, emini, entur
Present
Or/r, ris/re, tur, mur, mini, ntur
Perfect
4PP (-us -a -um) + sum, es, est
4PP (-i -ae -a) + sumus, estis, sunt
Pluperfect
4PP (-us -a -um) + eram, eras, erat
4PP (-i -ae -a) + eramus, eratis, erant
Future perfect
4PP (-us -a -um) + ero, eris, erit
4PP (-i -ae -a) + erimus, eritis, erunt