174. The parent (Indo-European) speech from which Latin comes had two main classes of verbs:

1. Thematic Verbs, in which a so-called thematic vowel (^e/o, in Latin ⁱ/u) appeared between the root and the personal ending.
   

   leg-i-tis (for †leg-e-tes)
   leg-u-nt (for †leg-o-nti)¹

2. Athematic Verbs, in which the personal endings were added directly to the root.

   es-t, es-tis (root ES)²
   dă-mus (dō, root DA)
   fer-t (ferō, root FER)

Of the Athematic Verbs few survive in Latin, and these are counted as irregular, except those which have been forced into one of the four “regular” conjugations. Even the irregular verbs have admitted many forms of the thematic type.

Of the Thematic Verbs a large number remain. These may be divided into two classes:

1. Verbs which preserve the thematic vowel e or o (in Latin i or u) before the personal endings. These make up the 3rd Conjugation. The Present stem is formed in various ways (§ 176 below), but always ends in a short vowel ^e/_o (Latin ⁱ/_u).
   

   tegō (stem teg^e/_o-)
   sternimus (stem stern^e/_o-) for †ster-no-mos
   plectunt (stem plect^e/_o-) for †plec-to-nti

   So nōscō (stem gnōsc^e/_o-) for gnō-sc-ō. Verbs like nōscō became the type for a large number of verbs in -scō, called inceptives (§ 263.1).

2. Verbs which form the present stem by means of the suffix y^e/_o-, which already contained the thematic vowel ^e/_o. Verbs of this class in which any vowel (except u) came in contact with the suffix y^e/_o- suffered contraction so as to present a long vowel ā-, ē-, ī-, at the end of the stem. In this contraction the thematic ^e/_o disappeared. These became the types of the 1st, 2nd, and 4th conjugations respectively. In imitation of these long vowel stems numerous verbs were formed by the Romans themselves (after the mode of formation had been entirely forgotten) from noun and adjective stems. This came to be the regular way of forming new verbs, just as in English the borrowed suffix -ize can be added to nouns and adjectives to make verbs.
   

   macadamize, modernize

Thematic verbs of the second class in which a consonant or u came into contact with the suffix y^e/_o- suffered various phonetic changes. Such verbs fall partly into the 3rd Conjugation—giving rise to an irregular form of it—and partly into the 4th, and some have forms of both.

(cōn)spiciō (-spicĕre) for †spekyō
veniō (venīre) for †(g)vem-yō

cupiō, cupĕre  BUT  cupīvī

orior, orĭtur  BUT  orīrī

Note, however,

pluō (pluere) for †plu-yō

and thus,

acuō (acuere) for †acu-yō

by analogy.

In all these cases many cross-analogies and errors as well as phonetic changes have been at work to produce irregularities. Hence has arisen the traditional system which is practically represented in §§ 175-176 below.

175. The Present Stem may be found by dropping -re in the Present Infinitive.

amā-re, stem amā-
monē-re, stem monē-
tegĕ-re, stem tegĕ-
audī-re, stem audī-

176. The Present Stem is formed from the Root in all regular verbs in one of the following ways.

a. In the 1st, 2nd, and 4th conjugations, by adding a long vowel (ā-, ē-, ī-) to the root, whose vowel is sometimes changed.

vocā-re (VOC)
monē-re (MEN, cf. meminī)
sopī-re (SOP)³

Note— Verb stems of these conjugations are almost all really formed from noun stems on the pattern of older formations (see § 174, above).

b. In the 3rd Conjugation, by adding a short vowel ^e/_o⁴ to the root. In Latin this ^e/_o usually appears as ⁱ/_u, but e is preserved in some forms.

tegi-s (root TEG)
ali-tis (AL)
regu-nt (REG)

BUT
tegĕ-ris (tegĕ-re)
alĕ-ris

1. The stem vowel ^e/_o (ⁱ/_u) may be preceded by n, t , or sc.⁵
   

   tem-ni-tis, tem-nu-nt, tem-nĕ-ris (TEM)
   plec-ti-s (PLEC)
   crē-sci-tis (CRĒ)

2. Verbs in -iō of the 3rd Conjugation (capiō, capĕre) show in some forms an ibefore the final vowel of the stem.
   

   cap-i-unt (CAP)
   fug-i-unt (FUG)

c. The root may be changed:

1. By the repetition of a part of it (reduplication).
   

   gi-gn-e-re (GEN)

2. By the insertion of a nasal (m or n).
   

   find-e-re (FID)
   tang-e-re (TAG)

d. In some verbs the Present stem is formed from a noun stem in u-

statu-e-re (statu-s)
aestu-ā-re (aestu-s)
cf. acuō, acuere⁶

Note 1— A few isolated forms use the simple root as a present stem.

fer-re, fer-t
es-se
vel-le
vul-t

These are counted as irregular.

Note 2— In some verbs the final consonant of the root is doubled before the stem vowel.

pell-i-tis (PEL)
mitt-i-tis (MIT)

e. Some verbs have roots ending in a vowel. In these the Present stem is generally identical with the root.

da-mus (DA)
flē-mus (stem flē-, root form unknown)⁷

But others, as rui-mus (RU), are formed with an additional vowel according to the analogy of the verbs described in d.

Note— Some verbs of this class reduplicate the root: as, si-st-e-re (STA, cf. stāre).

Footnotes