In Italian, all consonants except h can be doubled. Double consonants (i consonanti doppie) are pronounced much more forcefully than single consonants. With double f, l, m, n, r, s, and v, the sound is prolonged; with double b, c, d, g, p, and t, the stop is stronger than for the single consonant. Double z is pronounced almost the same as single z. Double s is always unvoiced.
Double consonant examples:
Italian
English
babbo
dad
fetta
slice
evviva
hurrah
bistecca
beefsteak
mamma
mama
albicocca
apricot
bello
beautiful
filetto
filet
anno
year
assai
a lot
basso
short
ragazzo
boy
ferro
iron
pennello
paint brush
espresso
espresso coffee
tavolozza
palette
spaghetti
spaghetti
cavalletto
easel
Most Italian words end in a vowel.
Diphthongs (i dittonghi) are two vowels fused to emit a single sound. A diphthong is formed when an unstressed i or u combines with another vowel (a, e, o) or when the two vowels combine with each other, in which case either the i or u may remain unstressed. In diphthongs, unstressed i and u become semivowels approximating in sound the English consonants y and w, respectively.
Diphthong examples:
Italian
English
ieri
yesterday
buono
good
fiore
flower
chiuso
closed
invidia
envy
più
more
Tripthongs also exist. These are sequences of three vowels with a single sound, usually a diphthong followed by an unstressed i.
Italian
English
tuoi
yours
miei
mine
buoi
oxen
pigliai
I took
Italian has numerous words that contain sequences of vowels. The following words are not triphthongs (which are infrequent), but sequences of a vowel and a diphthong.
Italian
English
noia
boredom
febbraio
February
baia
bay
fioraio
florist
Each of the words below has a sequence of two diphthongs:
Italian
English
ghiaia
gravel
muoio
I die
acquaio
sink
gioiello
jewel
From:https://www.dbfei.com/Article/yidaliyu/201311/6989.html