The book focuses on the linguistic phenomenon known as Jespersen's cycle in the dialects of Veneto, in northern Italy. Different perspectives of the emerging negator are explored: ranging from meaning, phonetic properties to the role of a focal feature. The book novelty lies in the use of acoustic data to investigate the diachrony of negation. It is shown that prosody plays a role in grammaticalization, cueing (in)stability in the reanalysis from a focal negator to a standard negation marker. The implications of this study promise new research avenues, showing the advantages of synchronous variation to inform diachrony and proposing that phonetic variation may be crucial in syntactic change.