Proto-Indo-European root

Typically, a root plus a suffix forms a stem, and adding an ending forms a word. \underbrace{\underbrace{\mathrm{root+suffix}}_{\mathrm{stem}} + \mathrm{ending}}_{\mathrm{word}} For example, '[they (sg.)] bear' can be split into the root 'to bear', the suffix which governs the imperfective aspect, and the ending , which governs the present tense, third-person singular. The suffix is sometimes missing, which has been interpreted as a zero suffix. Words with zero suffix are termed root verbs and root nouns. An example is '[I] am'. Beyond this basic structure, there is the nasal infix which functions as a present tense marker, and reduplication, a prefix with a number of grammatical and derivational functions. Finite verbs Verbal suffixes, including the zero suffix, convey grammatical information about tense and aspect, two grammatical categories that are not clearly distinguished. Imperfective (present, durative) and perfective aspect (aorist, punctual) are universally recognised, while some of the other aspects remain controversial. Two of the four moods, the subjunctive and the optative, are also formed with suffixes, which sometimes results in forms with two consecutive suffixes: > '[they (sg.)] would bear', with the first being the present tense marker, and the second the subjunctive marker. Reduplication can mark the present and the perfect. Nouns and adjectives Nouns usually derive from roots or verb stems by suffixation or by other means. (See the morphology of the Proto-Indo-European noun for some examples.) This can hold even for roots that are often translated as nouns: , for example, can mean 'to tread' or 'foot', depending on the ablaut grade and ending. Some noun stems like '''' 'lamb', however, do not derive from known verbal roots. In any case, the meaning of a noun is given by its stem, whether this is composed of a root plus a suffix or not. This leaves the ending, which conveys case and number. Adjectives are also derived by suffixation of (usually verbal) roots. An example is 'begotten, produced' from the root 'to beget, to produce'. The endings are the same as with nouns. Infinitives and participles Infinitives are verbal nouns and, just like other nouns, are formed with suffixes. It is not clear whether any of the infinitive suffixes reconstructed from the daughter languages (, , , among others) was actually used to express an infinitive in PIE. Participles are verbal adjectives formed with the suffixes (active imperfective and aorist participle), (perfect participle) and or (mediopassive participle), among others. ==Shape of a root==

In its base form, a PIE root consists of a single vowel, preceded and followed by consonants. Except for a very few cases, the root is fully characterized by its consonants, while the vowel may change in accordance with inflection or word derivation. Thus, the root can also appear as , with a long vowel as or , or even unsyllabic as , in different grammatical contexts. This process is called ablaut, and the different forms are called ablaut grades. The five ablaut grades are the e-grade, o-grade, lengthened e- and o-grades, and the zero-grade that lacks a vowel. In linguistic works, is used to stand in for the various ablaut grades that the vowel may appear in. Some reconstructions also include roots with as the vowel, but the existence of as a distinct vowel is disputed; see Indo-European ablaut: a-grade. The vowel is flanked on both sides by one or more consonants; The latter type always had a long vowel ( 'to put', 'to grow', 'to give'), while this restriction did not hold for vowel-initial roots ( 'to eat', 'to drive', 'to smell'). Laryngeal theory can explain this behaviour by reconstructing a laryngeal following the vowel (, , , resulting in a long vowel) or preceding it (, , , resulting in a short vowel). These reconstructions obey the mentioned rules. Sonority hierarchy When the onset or coda of a root contains a consonant cluster, the consonants in this cluster must be ordered according to their sonority. The vowel constitutes a sonority peak, and the sonority must progressively rise in the onset and progressively fall in the coda. PIE roots distinguish three main classes of consonants, arranged from high to low sonority: • Non-labial sonorants , denoted collectively as . • Labial sonorants , denoted collectively as . • Obstruents, denoted collectively as . These include three subgroups: • Plosives (voiceless , voiced , and aspirated ), denoted collectively as . • Sibilant . • Laryngeals , denoted collectively as . The following rules apply: • A laryngeal may appear before or after any obstruent other than another laryngeal. Examples are 'to grab', 'to fly', 'to dry', 'to pour, rain', 'to awake', and 'to be silent'. An additional constraint prohibited roots containing both a voiced aspirated and a voiceless plosive (*), unless the latter occurs in a word-initial cluster after an (e.g. 'to stiffen'). Taken together with the abundance of -type roots, it has been proposed that this distribution results from a limited process of voice assimilation in pre-PIE, where a voiceless stop was assimilated to a voiced aspirate, if another one followed or preceded within a root. Their role in PIE phonotactics is unknown. Roots like "to perish" apparently violate the phonotactical rules, but are quite common. Some roots cannot be reconstructed with an ablauting , an example being 'to grow, to become'. Such roots can be seen as generalized zero grades of unattested forms like *, and thus follow the phonotactical rules. Some roots like 'to sneeze' or 'to duck' do not appear to follow these rules. ==Lexical meaning==

The meaning of a reconstructed root is conventionally that of a verb; the terms root and verbal root are almost synonymous in PIE grammar. This is because, apart from a limited number of so-called root nouns, PIE roots overwhelmingly participate in verbal inflection through well-established morphological and phonological mechanisms. Their meanings are not always directly reconstructible, due to semantic shifts that led to discrepancies in the meanings of reflexes in the attested daughter languages. Many nouns and adjectives are derived from verbal roots via suffixes and ablaut. Nevertheless, some roots did exist that did not have a primary verbal derivation. Apart from the aforementioned root nouns, the most important of these were the so-called Caland roots, which had adjectival meaning. Such roots generally formed proterokinetic adjectives with the suffix , thematic adjectives in and compounding stems in . They included at least 'red', 'white', 'deep' and 'heavy'. Verbal roots were inherently either imperfective or perfective. To form a verb from the root's own aspect, verb endings were attached directly to the root, either with or without a thematic vowel. as detailed in Proto-Indo-European verb. The characterised imperfective stems are often different in different descendants, but with no association between certain forms and the various branches of Indo-European, which suggests that a number of aspects fell together before PIE split up. ==Creation of new roots==

Roots were occasionally created anew within PIE or its early descendants. A variety of methods have been observed. Root extensions Root extensions are additions of one or two sounds, often plosives, to the end of a root. These extensions do not seem to change the meaning of a root, and often lead to variant root forms across different descendants. The source and function of these extensions is not known. An example of such a pair of roots, both meaning 'to increase, to enlarge': • > Gothic 'to grow', Ancient Greek () 'to increase'. • > Gothic 'to increase, to grow', Latin 'to increase', Lithuanian 'to grow'. Another example concerns the root 'sky', which formed a vṛddhi derivative in this way: The oblique stem alternant was then reinterpreted as the e-grade of a new root, which formed a new neuter s-stem , a formation which is only created from roots. ==See also==