Proto-Indo-European Verbs - Overview

Overview

All of the older Indo-European languages show a complex system of verb conjugation, with verbs conjugated across multiple categories. In general, the following categories can be reconstructed for Proto-Indo-European (excluding Hittite and other Anatolian languages) in the traditional Cowgill-Rix system, although some categories (e.g. the dual) tended to drop out in time, while some languages innovated new categories (e.g. the future tense):

• Person: 1st, 2nd, 3rd
• Number: singular, dual, plural
• Voice: active, mediopassive (or "middle")
• Mood: indicative, subjunctive, optative, imperative, possibly also injunctive (used for "gnomic" statements expressing general truths or unchanging facts)
• Tense/Aspect: present, imperfect, aorist, perfect

The original interpretation of the tense/aspect categories has been a thorny issue; see below. The traditional names follow the usages of these forms in Ancient Greek, where the imperfect generally indicates an ongoing or repeated past action, the aorist a single past action viewed in its entirety, and the perfect as a past action with present relevance. They are sometimes compared, respectively, with the English forms "I was doing, I did, I have done", or (even more accurately) the Spanish forms "(yo) hacía, hice, he hecho". However, the meaning of these forms is somewhat different in Sanskrit, and even in Ancient Greek the canonical meanings only apply in finite verbs in the indicative mood; the categories of present, aorist and perfect also exist in other moods and in participles and infinitives but in these cases have only aspectual values.

Verbs could be formed according to multiple conjugations, each with its own way of constructing a given category. In the most conservative languages (e.g. Ancient Greek, Sanskrit, Tocharian, Old Irish), there is a separate set of conjugational classes for each of the tense/aspect categories, with no general relationship obtaining between the class of a given verb in one category relative to another. The result is that verbs must be described by a set of principal parts, each listing the method of forming a given category in that verb. There was a gradual tendency to regularize this system into a single set of global conjugations, which was partly complete in Latin (although not in Class III, the -ere verbs), and mostly complete in Germanic. Conversely, the oldest stages of the most conservative languages (esp. Vedic Sanskrit) reveal clear remains of an even less organized system, where a given verb root might have multiple ways, or no way at all, of being conjugated in a given tense/aspect category — sometimes with meanings that differ in unpredictable ways. This clearly suggests that the tense/aspect categories originated as separate lexical verbs, part of a system of derivational morphology (compare the related verbs "to rise" and "to raise", or the abstract nouns "produce", "product", "production" derived from the verb "to produce"), and only gradually became integrated into a coherent system of inflectional morphology, which was still incomplete at the time of the proto-language.

There were also a number of secondary formations, e.g. causative ("I had someone do something"), iterative/inceptive ("I did something repeatedly"/"I began to do something"), desiderative ("I want to do something"), which are distinguished from the "primary" formations by the fact that they generally are part of the derivational rather than inflectional morphology system in the daughter languages — although, as mentioned above, there was no clear boundary between the derivational and inflectional system of verbs in PIE. Not surprisingly, some of these formations have become part of the inflectional system in particular daughter languages. Probably the most common example is the future tense, which exists in many daughter languages but in forms that are not cognate, and tend to reflect either the PIE subjunctive or a PIE desiderative formation.

The methods of forming a given verb class in a given category are also complex and variable. In general, a given verb form can be described as a combination of three parts: ROOT/ABLAUT — SUFFIX — ENDING. The first two parts together (ROOT/ABLAUT — SUFFIX) are known as the stem. The ending generally indicates person, number and voice, while the stem generally indicates the verb class and category (i.e. mood and tense/aspect). A given class/category combination usually forms its stem using a combination of three types of root modifications:

• Adding a suffix.
• Changing the ablaut of the root. The ablaut is the type of vowel used in the verb root: generally, either e, o, ē, or no vowel (the "zero grade"). For some class/category combinations (particularly the "athematic" types; see below), there is also ablaut variation within a given paradigm. The most common case is for a "stronger" variant to be used in the active singular, while a "weaker" variant is used elsewhere in the paradigm. Examples of such ablaut variations are e or o vs. no vowel, and ē vs. e (so-called Narten classes).
• Changing the position of the stress, usually either on the root or suffix. Zero-grade ablaut roots are generally unstressed (i.e. the stress is on the suffix), while the other grades are generally stressed; but, naturally, with some exceptions.

In addition, some verb classes use additional types of root modification:

• The n-infix type of present class inserts an n within the root, before the last consonant.
• A number of different classes have reduplication, i.e. an additional syllable is prefixed onto the root, consisting of a copy of the first root consonant followed by a vowel e or i.

Note that this means that a given verbal category might form its stem in one of many quite different ways, sometimes with different endings. In addition, sometimes the identical stem formation is used across different class/category combinations. For example, the PIE aorist is usually formed in one of the following ways:

• The root aorist, which adds athematic endings directly onto the root, with e/zero ablaut within the paradigm: e.g. *leikʷ-t "he left" from root *leikʷ.
• The sigmatic aorist, which uses a suffix -s along with athematic endings and ē/e ablaut within the paradigm: e.g. *dēiḱ-s-t "he pointed out" from root *deiḱ.
• The reduplicated aorist, which uses reduplication along with athematic endings and e/zero ablaut within the paradigm.
• The thematic aorist, which adds thematic endings onto the root, with no ablaut within the paradigm: e.g. *h₁ludh-et "he went" from root *h₁leudh, with zero-grade ablaut.

All four methods of forming the stem are also found in the present, although sometimes with different ablaut. Although the present and aorist use different endings, the imperfect is formed using the present stem and the same endings as in the aorist; as a result, present and aorist stems are generally formed in different ways, to avoid ambiguity.

As just indicated, there are multiple sets of endings, depending on both the class and category, and in some cases distinct endings may be the only thing distinguishing one category from another. Endings are characterized as primary vs. secondary, and as thematic vs. athematic. Primary endings are generally used in the present indicative and throughout the subjunctive, while secondary endings are used elsewhere. In many cases, the primary endings are distinguished relative to the secondary endings by an additional suffix (originally -i in the active and -r in the mediopassive, although the majority of subfamilies generalized -i to the mediopassive as well). Athematic endings are added directly onto the stem, while thematic endings are usually the same as the athematic endings but with an additional "theme vowel" (either e or o) added between stem and ending. There are also some unpredictable variations among different sets of endings, e.g. first singular active athematic *-mi but thematic *-oh₂. Finally, there is an additional set of endings specific to the perfect, and another set specific to the imperative.