Proto-Indo-European verbs reflect a complex system of morphology, more complicated than the substantive, with verbs categorized according to their aspect, using multiple grammatical moods and voices, and being conjugated according to person, number and tense. In addition to finite forms thus formed, non-finite forms such as participles are also extensively used.
The verbal system is clearly represented in Ancient Greek and Vedic Sanskrit, which closely correspond in nearly all aspects of their verbal systems, and are two of the most well-understood of the early daughter languages of Proto-Indo-European.
Basics The reconstruction of verb conjugation in Proto-Indo-European is controversial. The system described here is known as the "Cowgill–Rix" system, which explains fairly well the data found in most subfamilies of Indo-European. However, this reconstruction encounters significant difficulties when applied to the Anatolian and to some extent the Tocharian branch. For this reason, this system is often thought to have formed not in PIE proper, but at a later stage, after Anatolian and possibly Tocharian had split off. Even so, there is no consensus concerning what the ancestral system of verb conjugation prior to the split-off of Anatolian looked like, and which Anatolian differences are innovations vs. archaisms.Fortson, pp. 88-91.
The Cowgill-Rix system involves the interplay of six dimensions (number, person, voice, mood, aspect and tense) with the following variables:
+ 3 numbers singular, dual, plural 3 persons first, second, third 2 voices active, middle (or medio-passive) 4-5 moods indicative, subjunctive, optative, imperative, possibly injunctive 3 aspects imperfective ("present"), perfective ("aorist"), stative ("perfect") 2 tenses present, past ("imperfect")
Further, participles can be considered part of the verbal systems although they are not verbs themselves, and as with other PIE nouns, they can be declined across seven or eight cases, for three genders and three numbers.Fortson, §5.60.
Building blocks
Roots
The starting point for the morphological analysis of the PIE verb is the root. PIE roots are morphemes with lexical meanings, which usually consist of a single vowel flanked by one or more consonants arranged to very specific rules.
Stems and stem formation Before the final endings—to denote number, person, etc.—can be applied, additional elements () may be added to the root (). The resulting component here after any such affixion is the stem, to which the final endings () can then be added to obtain the conjugated forms.
Athematic and thematic stems
Verbs, like nominals, made a basic distinction based on whether a short, ablauting vowel -e- or -o-, called the thematic vowel was affixed to the root before the final endings added.Fortson, 2nd Ed. §4.22.
In the case of the thematic conjugations, some of the endings differed depending on whether this vowel was present or absent, but by and large the endings were the same for both types.
The athematic system is much older and exhibits ablaut within the paradigm. In the descendant languages, athematic verbs were often extended with a thematic vowel, likely because of the complications resulting from the consonant clusters formed when the mostly consonant-initial endings were added directly onto the mostly consonant-final stems.Fortson, 2nd Ed. §4.23.
Consequently, the athematic verbs became a non-productive relic class in the later Indo-European languages. In groups such as Germanic and Italic, the athematic verbs had almost gone entirely extinct by the time of written records, while Sanskrit and Ancient Greek preserve them more clearly.
Proposed endings
At least the following sets of endings existed: Primary ("present") endings used for: Present tense of the indicative mood of imperfective verbs. Subjunctive mood Secondary ("past" or "tenseless") endings used for: Past tense of the indicative mood of imperfective verbs. Indicative mood of perfective verbs. Optative mood Stative endings used for Indicative mood of stative verbs. Imperative endings used for Imperative mood of all verbs.
Note that, from a diachronic perspective, the secondary endings were actually the more basic ones, while the primary endings were formed from them by adding a suffix, originally -i in the active voice and -r in the middle voice.
The more central subfamilies of Indo-European have innovated by replacing the middle-voice -r with the -i of the active voice.
Traditional accounts say that the first-person singular primary ending is the only form where athematic verbs used a different ending from thematic verbs. Newer accounts by and are similar, with the proto-forms modernized using laryngeal notation.
The linguist Andrew Sihler, however, notes that many of the most archaic languages have third-person singular forms missing a t and proposes an alternative t-less thematic ending along with the standard ending. Greek and Balto-Slavic have t-less forms in thematic actives, whereas Vedic and Hittite have t-less athematic middle forms.
uses the t-less forms as the starting point for a radical rethinking of the thematic endings, based primarily on Greek and Lithuanian. These proposals are still controversial, however.
Active eventive endings
Primary Singular 1st , , , , 2nd , 3rd , , Dual 1st 2nd / 3rd Plural 1st , 2nd 3rd , Secondary Singular 1st 2nd 3rd Dual 1st 2nd 3rd Plural 1st 2nd 3rd , Imperative Singular 1st — — — — 2nd , , , , , , 3rd , , (?), Dual 1st — — — — 2nd ? ? ? 3rd ? ? ? Plural 1st — — — — 2nd , 3rd , (?) Participle *-ont- ~ *-nt-, *-ont- *-ent- ~ *-nt-, *-ont- *-ent- ~ *-nt-, *-ont- *-ont- ~ *-nt-, *-ont-
Middle eventive endings
Primary Singular 1st — 2nd — 3rd — Dual 1st ? — ? 2nd ? — ? ? 3rd ? — ? ? Plural 1st — ? 2nd — ? 3rd , — , Secondary Intransitive Transitive Singular 1st 2nd 3rd Dual 1st ? ? 2nd ? ? ? ? 3rd ? ? ? ? Plural 1st ? 2nd ? 3rd , , Imperative Intransitive Transitive Singular 1st — — — — 2nd ? — ? ? 3rd ? ? ? ? Dual 1st — — — — 2nd ? ? ? ? 3rd ? ? ? ? Plural 1st — — — — 2nd — ? 3rd ? ? ? ? Participle *-m(e)no- *-mh₁no- *-m(e)no-, *-mh₁no- *-mh₁no-
Stative endings
Indicative Singular 1st 2nd 3rd Dual 1st ? ? ? 2nd ? ? ? ? 3rd ? ? ? ? Plural 1st 2nd 3rd , Participle *-wos- ~ *-us- *-wos- ~ *-us- *-wos- ~ *-us- *-wos- ~ *-us-
A second conjugation has been proposed in Jay Jasanoff's h₂e-conjugation theory. Svensson (2001) suggests *-h₂éy for the second and third dual stative endings, on the basis of evidence from Indo-Iranian, Tocharian, and Gaulish.
Verb aspects The standard reconstruction of Proto-Indo-European verbal morphology outlines a system primarily defined by aspectual opposition rather than tense. However, in the most ancient attested Indo-European languages, this system had largely faded and a new emphasis on a past—non-past distinction had emerged. The most archaic known Indo-European language, Hittite, primarily distinguishes between past and non-past forms and bears no trace of any earlier aspectual opposition. There are other Indo-European languages that have largely simplified their verbal morphologies, though it is unusual for an exceptionally ancient Indo-European language such as Hittite to bear little trace of the presumed importance of aspect within PIE. According to the linguists Jesse Lundquist and Anthony Yates, the evidence from Hittite implies the existence of an earlier system primarily centered around lexical rather than grammatical aspect. Yates and Lundquist note the wide variety of verbal classes in Core Indo-European that appear to lack much semantic difference, implying a merger of earlier formations.
Proto-Indo-European verbs belonged to one of three aspect classes: Stative verbs depicted a state of being. Eventive verbs expressed events. These could be further divided between: Perfective verbs depicting actions viewed as punctual, an entire process without attention to internal details, completed as a whole or not completed at all. No distinction in tense was made. Imperfective verbs depicting durative, ongoing or repeated action, with attention to internal details. This included the time of speaking; separate endings were used for present or future events in contrast to past events.
The terminology around the stative, perfective and imperfective aspects can be confusing. The use of these terms here is based on the reconstructed meanings of the corresponding forms in PIE and the terms used broadly in linguistics to refer to aspects with these meanings.
In traditional PIE terminology, the forms described here as stative, perfective and imperfective are known as the perfect, aorist and present systems:
Stative = Perfect Perfective = Aorist Imperfective = Present
The present/imperfective system in turn can be conjugated in two tenses, described here as present and past but traditionally known as present and imperfect. The traditional terms are based on the names of the corresponding forms in Ancient Greek (also applied to Sanskrit), and are still commonly encountered. Furthermore, there is a separate secondary-verb form commonly known as the "stative" and marked by a suffix *-eh₁-, which has no connection with the stative/perfect described here.
The following table shows the two systems of terminology.
Process Aspect Aspect (traditional name) Tense Tense (traditional name) Stative Stative Perfect (unmarked) Perfect tense Eventive Perfective, punctual Aorist (unmarked) Aorist tense Imperfective, durative Present Present Present tense Past or tenseless Imperfect tense
In Proto-Indo-European, the aspects had no tense meaning, which later developed in the descendant languages. In Ancient Greek, for example, the perfect carried the meaning of a state resulting from a past action, but the PIE stative referred to the state alone. Likewise, the aorist, though having a tense-like meaning in Ancient Greek, had none in PIE. Perfective and stative verbs were effectively tenseless, or indifferent to time.
Eventive verbs
The perfective ("aorist") and imperfective ("present") aspect classes are together known as eventive, or verbs that depict events, to distinguish them from stative (verbs that depict a state of being). Broadly, the imperfective described actions with internal structure, be they continuous, iterative, habitual, or any other type. Sihler generalizes the meaning of the imperfective class as durative, meaning that it encompassed continuous actions. This class was further subdivided into present imperfective and past imperfective categories, the former of which denoted actions occurring during the present or the future (i.e., is doing), whereas the latter described actions that were occurring continuously in the past (i.e., was doing). In contrast, the perfective class denoted events without any such structure, perhaps either due to the speaker's lack of care for or knowledge of these details. Sihler ascribes a punctual value to the aorist, meaning that it referred to actions that did not necessarily span over extended periods of time. Since the punctual aspect is generally incompatible with descriptions of present occurrences, it is likely that the aorist largely described past actions.