La Spezia–Rimini Line

The line divides northern and central Italy, running approximately between the cities of La Spezia and Rimini (or, according to some linguists, between Massa and Senigallia, which lie about 40 kilometres further to the south).

[citation needed] The three isoglosses considered traditionally are: To these should be added a fourth criterion, generally more decisive than the phenomenon of voicing: North and west of the line (excluding all Northern Italian varieties) the plural of nouns was adapted from the Latin accusative case, and is marked with /s/ regardless of grammatical gender or declension.

However, the differentiation is not totally systematic, and there are exceptions to the isogloss: Gascon dialects in south-west France and Aragonese in northern Aragon, Spain (geographically Western Romance) also retain the original Latin voiceless stop between vowels.

The presence in Tuscany and elsewhere below the line of a small percentage but large number of voiced forms both in general vocabulary and in traditional toponyms also challenges its absolute integrity.

Romanian, which on the basis of lack of voicing, i-plurals and palatalisation to /tʃ/ is classified with Central and Southern Italian, has experienced simplification of geminates, a defining characteristic of Western Romance, after the rhotacism of intervocalic /l/.