Double consonants

Syntetic gemination (raddoppiamento sintattico)

"Syntactic" means that gemination spans word boundaries, as opposed to word-internal geminate consonants as in [ˈɡatto] "cat" or [ˈanno] "year". In standard Italian, syntactic doubling occurs after the following words (with exceptions described below):

All stressed ("strong") monosyllables (monosillabi forti) and some unstressed ("weak") monosyllables (monosillabi deboli):
a, blu, che, ché, chi, ciò, da, dà, dì, do, e, è, fa, fra, fu, già, giù, ha, ho, la (noun), là, lì, ma, me (stressed), mi (noun), né, o (conjunction), più, può, qua, qui, re, sa, se (conjunction), sé, si (noun), sì, so, sta, sto, su, sù, te (stressed), tè, tra, tre, tu, va, etc

Example: Andiamo a casa [anˈdjaːmo a‿kˈkaːza], 'Let's go home'

all polysyllables stressed on the final vowel (oxytones)

Example: Parigi è una città bellissima [paˈriːdʒi ɛ una tʃitˈta‿bbelˈlissima], 'Paris is a very beautiful city'

a few paroxytones (words with stress on the second-last syllable) when they are not substantivized: come, dove (ove), qualche, sopra (sovra)

Example: Come va? [ˈkome‿vˈva], 'How are you?'

Exceptions

It does not occur in the following cases:

A pause is at the boundary of words in question. In particular, initial gemination may be conditioned by syntax, which determines the likelihood of pause. For example, in the phrase La volpe ne aveva mangiato metà prima di addormentarsi ('The fox had eaten half of it before falling asleep'), there is no gemination after metà if there is even a slight pause, as prima is part of the adjunct, a sentence element that is easily isolated phonologically from the main clause within the prosodic hierarchy of the phrase.[4] The stressed final vowel is lengthened. A sharp break or change occurs in the pitch on the word boundary. There are other considerations, especially in various dialects, so that initial gemination is subject to complicated lexical, syntactic and phonological/prosodic conditions.

Phrasal doubling

weak and strong monosyllables. Weak monosyllables: mi, la, Strong monosyllables: Ah, piú, oh, lá, me, two syllable word that causes a phrasal doubling: dove mi spinse = ddove mmi spinse If you have an accent on the final syllable, the next consonant gets doubled Ah, piú non vive. What do we double? Not both, because that becomes inelegant. Either: Ah, ppiú non vive. or: Ah, piú nnon vive.