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Using patterns: Latin verbs: Part 2: Principal Parts for 3rd conjugation

December 4, 2014

In standard terminology for Latin grammar, the terms first conjugation, second conjugation and fourth conjugation each refer to a class of verbs characterized by a long vowel at the end of the root or stem (formed by dropping -re from the end of the infinitive); the long vowel in each is respectively a, e and i. Verbs in the other vowels o and u do not occur.

The third conjugation deals with the short vowels. The vowel a does not occur short; if it did in a previous stage of Latin’s development, then those vowels had lengthened by the Classical period. Indeed, all infinitives of the third conjugation have a short vowel e in the infinitive. Yet a large class of third conjugation verbs preserve an i in the stem in at least the first principal part. My opinion is that in some earlier pre-Classical stage of Latin, these i-stem third conjugation verbs were associated with a short i which mutated in the infinitive.


A good discussion of how the four classes of verbs evolved into the Romance languages can be found here. The association of the third conjugation with short vowels e and possibly also i remains for all the languages discussed at the link: the five national Romance languages plus Sardinian, Catalan and Romansh. Occitan is a notable Romance language which is not discussed at that link but its verbs appear to have lost the distinction between second and third conjugation verbs in terms of Latin.

: end digression.

When applying the pattern for the principal parts, which takes the form

-o, -re, -vi, -tum

as established in a previous post about long vowel stems, the fact that short vowels (especially when unstressed as in this case) are highly mutable. Moreover they often influence mutations in adjacent consonants. (Latin stressed the penultimate syllable if it was either closed or has a long vowel but the ante-penultimate syllable otherwise.) Thus even the two classes of regular third conjugation verbs in Latin are irregular in the sense that the stem tends to change:

duc-o, duce-re, dux-i, duc-tum

capi-o, cape-re, cep-i, cap-tum.

In the first principal part, the short e of the root is absorbed into the long o of the conjugation suffix. The short i remains. In the second principal part, the short e remains but the short i is transmuted into a short e— effectively a neutral vowel. In the fourth principal part, both short vowels are simply dropped.

The third principal part (the first person singular active perfect form of the verb) often undergoes marked changes to the stem. The short vowel is almost always absorbed. If the semi-vowel u/v of the conjugation suffix is retained at all (which happens but is rare) it becomes strictly vocalic, i.e., u but not v.

What this means is that when learning Latin verbs, the third conjugation will usually require the most effort to learn. The phonological shifts do have patterns but familiarization with the principal parts of as large amount of Latin verbs will tend to impart an intuitive knowledge of those phonological patterns better than trying to consciously memorize them. When memorizing verbs in Latin, one should try to apply the Latin rules of syllable accentuation because that will help in the application of correct grammatical forms.

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