History of the english language

Simplification of Word Structure in Late Proto-Germanic.
Role of Stem-suffixes in the Formation of Declensions
Some changes in the morphological structure of the word in Late PG account for the development of an elaborate system of declensions in OG languages, and for the formation of grammatical endings. Originally, in Early PG the word consisted of three main component parts: the root, the stem-suffix and the grammatical ending. The stem-suffix was a means of word derivation, the ending - a marker of the grammatical form. In Late PG the old stem-suffixes lost their derivational force and merged with other components of the word, usually with the endings. The word was simplified: the three morpheme structure was transformed into a two-morpheme structure. The original grammatical ending, together with the stem-suffix formed a new ending.
The simplification of the word structure and the loss of stem-suffixes as distinct components was facilitated - or, perhaps, caused - by the heavy Germanic word stress fixed on the root. Most nouns and adjectives in PG, and also many verbs, had stem-forming suffixes; according to stem-suffixes they fell into groups, or classes: a-stems, i-stems, o-stems, etc. This grouping accounts for the formation of different declensions in nouns and adjectives, and for some differences in the conjugation of verbs. Groups of nouns with different stem-suffixes made distinct types of declension. The original grammatical endings were alike for most nouns, e.g. Nom, sg -z, Dat. -i, Ace. -rn. When these endings fused with different stem-suffixes, each group of nouns acquired a different set of endings. The division of nouns into declensions resting on the stem-suffixes is not peculiar to Germanic alone; it is also found in other IE languages (some types of declensions in Germanic correspond to certain declensions in non-Germanic languages, e.g. 6- stems correspond to the first declensions in Latin and Russian (their stem-suffix is -a: Germanic -0 has developed from IE -a; Germanic a-stems correspond to the second declension in Latin and in Russian (o-stems in both these languages, since IE [0] became [a] in Germanic).The Germanic languages preserved the old classification of nouns with great accuracy, added other distinctive features to the noun paradigms and, as a result, had a complicated system of noun declensions in the early periods of history.