The ending or inflexion
Stem (основа)-forming suffix
The root
Morphological structure of the word in Parent Indo-European language
The structure of the word in PIE was characterized by three morphological elements:
The root morpheme together with stem-forming suffix is termed the stem (основа). The stem maybe equal to the root as in simple words, or it may contain a root and word building suffixes (derivational suffixes) in derived words. It may have more than one root morpheme as in modern compound words. Later, in Common Germanic period in all Germanic languages the morphological structure of the word was simplified: the stem-forming suffix disappeared, fusing (смешиваться) either with the root of the word, or with the inflexion. When the stem-forming suffix blended with the root, the last letter of the root was modified and thus sometimes appeared such pairs of words, which come from the same Indo-European root but developed different meanings.
For example, the modern word “tide” and “time” origin from PIE root from “ti” (m,d) + e.
Parts of speech and grammatical categories in PIE
In PIE the noun, pronoun and adjective had the grammatical categories of gender, number, and case. Each noun in PGL belonged to one of the three genders: masculine, feminine, neuter. The gender distinction rested on grammatical but not on logical grounds, though sometimes it corresponded to the natural gender or sex. There were 3 numbers in PGL: the singular, the plural, and the dual numbers (двойственное число).
There were 7 or 8 cases in GPL:
1. Nominative case (именительный падеж)
2. Genitive case (родительный падеж)
3. Dative case (дательный падеж)
4. Accusative case (винительный падеж)
5. Ablative case (отложительный падеж)
6. Locative case (местный падеж)
7. Instrumental case (инструментальный падеж)
8. Vocative case (звательный падеж)
(Ablative was assimilated by the Genitive = Genitive; Locative coincided with Dative, Instrumental fused with the stronger cases + Dative.The most ancient and the most stable IE cases are: Nominative, Genitive, Dative Accusative.) Thus of 8 proto-IE cases OE kept only 4which were inherited from the CG. Original IE noun cases were weak enough to be lost practically in all branches of the family.
Old English: Nominative, Accusative, Dative, Genitive
Thus, of the 8 proto-Indo-European cases Old Englishkept only 4 cases which were inherited from the Common Germanic language: Nominative, Accusative, Dative, Genitive, in the majority of texts Nominative and Accusative had the same form. The noun was characterized by a highly developed system of declension (склонение), which rested on the Indo-European stems: a-stem, o-stem, i-stem. Later the morphological system of the noun in Germanic languages including English, was simplified, so that nowadays only some modern languages have preserved the system of declension, the paradigm of the noun, consisting of 3 categories, including Russian.
As to its phonetic system, here also the PIE differed from the historically transmitted IE languages , having its characteristic features in consonants, vowels and accentuation. Primitive IE was very rich in stops, the only fricative being [s] with its voiced allophone [z]. the vowel system was very much alike that of Greek. As to accentuation, the stress was shifted from one syllable to another according to definite rules, just as in modern Russian.
In historical times, close to the end of the first millennium B.C. the parent IE split into a variety of languages, each with its own peculiarities in sounds, in grammar and vocabulary. Thus, in all Germanic languages we observe a considerable simplification of the earliest morphological system: they preserve only some relics of the dual number, the system of 8 cases is reduced to 4-5 cases.