|The 1st Conjugation is the most predictable for perfect stems: all end in -av- (e.g. porto/portavi), except do/dedi and sto/steti.
||Perfect stems in the 2nd Conjugation end in -u- roughly half the time (e.g. timeo/timui, terreo/terrui) but otherwise vary (e.g. sedeo/sedi, rideo/risi).
||The 3rd Conjugation is the most unpredictable. An “s” sound is common (e.g. misi, scripsi, discessi, dixi), but practically all need to be learned as though additional vocabulary.
||The 4th Conjugation is either like audio/audivi or venio/veni (as in veni, vidi, vici), along with sentio/sensi
||Perfect stems in the 5th Conjugation are various, but a change of vowel to an -e- is common (e.g. facio/feci, capio/cepi, iacio/ieci)