Abstract 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 risi