Indo-European languages of the most archaic type, such as Old Indic and Ancient Greek, have rich fusional morphologies with predominant use of suffixation and ablaut as formal devices. The presence of cumulative inflectional morphs in final position is also a general IE feature.
A noteworthy property of the archaic IE morphological system is its root-based organization. This is well observable in Old Indo-Aryan, where the mental lexicon is largely made up of roots unspecified for word-class membership.
In the historical development of the different IE branches, recurrent phenomena are observed that lead to an increase in configurationality and a decrease in the degree of synthesis (use of adpositions at the expense of case forms, rise of auxiliaries and increasing employment of periphrastic morphology, creation of determiners). However, not all the documented developments can be subsumed under the rubric ‘morphological decay’: new synthetic verbal forms, which often coexist with the inherited ones, are often created via resynthesization of periphrases; new nominal case forms are sometimes created through univerbation of adpositional phrases; instances of prefixation recurrently arise from former compound structures consisting of adverb (‘preverb’) + verb.
The formation of inflectional paradigms with several mutually unpredictable subsections and of relatively complex systems of inflectional classes is also observed in various IE languages. The same holds for the rising of new patterns of morphophonological alternations, which often allow the preservation of several morphological oppositions even after the loss of inflectional endings. As a consequence, modern IE languages may exhibit higher degrees of fusionality, at least in specific morphological subsystems, than their diachronic foregoers.
In the various branches, the system of inflectional morphology could undergo several reshapings at the level of both the structure of grammatical categories and the formal organization of paradigms, sometimes with noteworthy typological changes. English poor morphology, Ossetic and New Armenian agglutinative nominal inflections, lack of verbal inflection of number, and presence of numeral classifiers in Eastern New Indo-Aryan varieties are among the examples of extreme departure from the ancient IE morphological type. A common development concerning word formation is the decline of the root-based organization of morphology.
Token frequency as a determinant of morphological change
