La Spezia-Rimini line
The La Spezia-Rimini line is generally taken to be the dividing line that separates the Western Romance languages, which pluralise by adding -s, from the Italo-Dalmatian and Eastern Romance languages, which pluralise by changing the final vowel.
There are also some key phonetic differences that broadly follow this isogloss, including:
- the palatalisation of c before e/i: north of the line it mostly palatalised to [(t)s] (except some Gallo-Italian languages immediately adjacent to this line); south it mostly palatalised to [tʃ]
- intervocalic stops /p, t, k/ which were unvoiced in Latin became voiced in most languages north of the line (with some exceptions in Aragonese and the Occitan dialect Gascon); south, they mostly remained voiceless
- most of the languages northwest of the line lost Latin’s geminate consonants (with some exceptions, like l·l in Catalan, and noting that the geminate consonants didn’t always merge with their ungeminated form but often palatalised like nn did to [ɲ] or ll to [ʎ]); southeast of the line, most languages kept geminate consonants (but Romanian didn’t)