Here’s a mnemonic device I wrote to help my students in Baby Latin to cope with one of the difficulties of the 3rd conjugation, namely the vowel shifts of the present tense:
- In conjugations 1 & 2
- (& also 4) the vowels are true.
- But conjugation 3’s unique:
- use I and U, since short E’s weak.
We use the infinitive, of course, to determine the conjugation of each verb, and in the 1st, 2nd, and 4th conjugations the vowel before the infinitive ending is used throughout the present tense. Verbs in -are show -a- (though it disappears before -o), and so on. But the 3rd conjugation often troubles students because the -e- of the infinitive is nowhere to be found.
It’s helpful to talk about the relative strength of the various vowels. The E of the 2nd and the I of the 4th remain even before the 1st person ending, for example. And these long vowels are short where Latin phonology requires it (before another vowel or before final -t or -nt).
But the 3rd conjugation is different precisely because the E is short. Rather than persist (be ‘true,’ as the rhyme says), it changes, and these changes are the same as those which students will see in the future tense.
The future tense marker of the 1st and 2nd conjugations is really -be-, with a short E, and this is why the endings go -bo, -bis, -bit / -bimus, bitis, -bunt. It’s no different from the present tense of the 3rd conjugation, where short E produces -o, -is, -it / -imus, -itis, -unt.
And while we’re on the subject, let’s just remember the mnemonic for the future tense endings of the various conjugations, which I give in a simple form than the usual:
- 1 & 2,
- -bo, -bi-, -bu-
- 4 & 3,
- -a- then -e-