All of the affirmative singular imperatives of regular verbs are formed by dropping the -re from the second principal part.
Why is it that, in the 3rd conjugation only, the affirmative plural imperative drops the -ere from the second principal part and then adds -ite instead of just dropping the -re and adding -te like in the other conjugations?

2 Answers 2


This has to do with the verbal conjugation system of Proto-Indo-European (PIE), the ancestor language of Latin. The Latin third conjugation is largely descended from so-called "thematic" PIE verbs. Thematic verbs are those which have a vowel, either e or o, between the verb root and the ending; this is known as the "thematic vowel". In this case, the vowel was e, so the 2pl. imperative would have ended in -e-te. This e later changed into Latin i by the regular sound change of "vowel reduction", in which basically all short vowels in non-initial open syllables changed into e.

It's not only the i of -ite that is descended from the PIE thematic vowel, but also the i that shows up elsewhere in the third conjugation present forms: ag-i-s, ag-i-t, etc.

(The other three conjugations, too, mostly continue PIE thematic verbs, but in those conjugations the thematic vowel eventually merged into the long vowel of the verb stem.)


I believe this is due to vowel reduction. Latin vowel reduction is complicated and there seem to be various processes involved; however, a common pattern is vowels turning to /i/.

Syllable and Segment in Latin, by Ranjan Sen (2015), describes a process called "Archaic Latin vowel reduction" whereby short vowels in internal (not initial or final) open syllables were generally all merged to a reduced vowel which became /i/ in Classical Latin. In internal open syllables before /r/, however, the reduced vowel became /e/ instead. This explains the difference between -ite and -ere.

I don't know what the original vowel was in third-conjugation verbs, but it seems like we would get this pattern no matter what it was. It seems to come from the Proto-Indo-European "thematic vowel" (for example, see this page from Allen and Greenough) which apparently could be -e- or -o-. I don't understand the details of its distribution; however, the -u- that appears in Latin verbs of the third declension before nasals in closed syllables (e.g. in third-person plural -unt) seems to descend from PIE -o-.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.