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Thirds, Part II: Third Conjugation Verbs

Last month, we dealt with those pesky third declension nouns. This month, we will take a look at third conjugation verbs.


For some reason, thirds are always a bit difficult in Latin. Please keep in mind that the Romans did not order declensions and conjugations; rather, those who were teaching the language to others gave them declension and conjugation numbers in order to teach them. It is comparable, perhaps, to us putting words into word families when teaching plurals or participles. Once things are sorted into groups, they are easier to learn.


Third conjugation verbs are grouped together because their infinitives (the second principal parts) end in –ere. Their first principal part ends in –o or –io (for third IO verbs). Their third principal parts end in the letter -i, but in general, they are variable. Their fourth principal parts end in either –sum or –tum. This poses the first challenge with regard to the third conjugation verbs: irregularities are common with respect to their principle parts and they simply must be memorized. However, as you and your students study the principal parts of third conjugation verbs, you will begin to notice the presence of some patterns. For example, there are verbs which lengthen the main vowel from their first principal part in their third principal part (e.g., agoagereēgi,actum) while others repeat the first syllable of the first principal part in the third principal part (curro, currere, cucurri, cursum). Of course, the best derivatives from Latin verbs seem to come from third conjugation, particularly from the fourth principal part.


There are two difficult aspects of conjugating verbs in the third conjugation:


  • • One is the fact that in the third conjugation the theme vowel (the vowel between the stem and the ending) for the present tense is an "i"* (and, for third plural, "u"). My students always ask me about this, and I say that I do not know why it is an "i." I remind them that there is an "i" in the word "third," and they may use that as a clue for remembering it. I have even gone so far as to say that they should picture the "e" they expect getting eaten by an "i." (*For example, the first conjugation ending for the infinitive is –are, and the theme vowel remains an "a" in the present tense conjugation. Consider laudare (to praise). Its present tense conjugation is laudo, laudas, laudat, ladamus, laudatis, laudant. The theme vowel remains an "a." Similarly, take a look at the second conjugation where the infinitive ending is –ēre. In that case, the theme vowel also remains an "e." Consider vidēre (to see). Its present tense conjugation is vidēo, vidēs, videt, vidēmus, vidētis, vident. Note that the theme vowel remains an "e." In contrast, however, examine the third conjugation, whose infinitive ends in –ere as well, but whose theme vowel changes from an "e" to an "i" in the present tense. Consider mittere (to send): mitto, mittis, mittit, mittimus, mittitis, mittunt. Note how the theme vowel becomes an "i" and in the third plural, a "u.")
  • • The other hard part is that the future tense does not have the endings "-bo, -bis, -bit, -bimus, -bitis, -bunt." Instead, these do not have a theme vowel, but have "-am, -es, -et, -emus, -etis, -ent." My Latin teacher from high school always reminded us that third and fourth conjugations have "no beaus/bo's in the future."


In summation, here are the three hard—but not insurmountable—characteristics of third conjugation verbs: the principal parts are highly irregular and generally must simply be memorized—but it helps to notice there are subtle patterns that can help; the present tense has an –i (and -u) instead of the –e you expect…however, we can memorize that fact quickly; the future does not have bo’s, but it still has the same personal endings upon which verbs are based  (-m,-s, -t, -mus,-tis,-nt).


God has given us the logic to sort out the third conjugation. It uses the same endings as the other conjugations for all the tenses except the future. It use the same principal parts for each tense; the perfect, pluperfect and future perfect, for instance, use the third principal part minus the –i. We just have to be mindful of third’s present theme vowel, its future endings, and its principal parts!


May God bless you in your studies and during this Christmas Season!

TIERS: challenge
CATEGORIES: Articles, Classical Christian Education, Rhetoric Stage (ages 14 to 18)

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