This article analyzes the process of diachronic changes in the morphological means of expression of the category of number in English and German from the point of view of the synergetic concept. The article provides an overview of factors that cause the process of unification of the means of expression of the morphological number category number. Scientific interest may be a comparison of the morphological systems of two genetically related languages that have completely different ways of development. The article contains a number of assumptions about the reasons of the typological differences in the morphology of the German and English languages. The subject of research are the evolutionary processes of the system of morphological means of expression in category of number and diachronic changes in the relationship of the language systems. The focus is on the morphological evolution of the morphological means in the number category in English and German, and provides an explanation of paradoxical phenomena related to the formation of the morphology in these languages on the basis of synergistic parameters. The author makes an attempt to discover cause-and-effect relationship in the language evolution and explore the mechanisms of morphological changes and proposes a model of synergy analysis of the evolution mechanism of language system during the process of unification of the morphologica means of expression of number category in English and German.