Chapter 15 outlines the linguistic respects in which related dialects were believed to vary, in contrast to distinct languages, during the early modern era. Initially, a Byzantine author was the main source of inspiration in describing dialect-level differences, primarily in Greek handbooks. It was only after 1650 that the levels of variation were treated in a more systematic fashion by non-Hellenists, too. The focus of attention was on the ways in which related dialects varied. The differences were, most scholars agreed, superficial, and mainly situated in pronunciation, letters, and the lexicon. There was, however, no linguistic domain in which related dialects were claimed to never demonstrate variation. Overall, the differences required for qualification as distinct languages attracted less attention. Yet many scholars agreed that substantial differences were needed, principally in the roots of words. Sometimes, unusual linguistic criteria were put forward, e.g. by Johann Georg Wachter and Ferdinando Galiani.