When not in the midst of a short-lived diet regime, I have the terrible habit of binging on chips (or crisps as they are known in the UK) and French fries. There is something about their salty greasiness that just hits the spot! The word for both of these irresistible junk foods in Italian is patatine.
The singular patatina, which is the diminutive of patata (potato), may refer to individual chips or fries, or any kind of small potato such as a new potato.
The easiest way to specify that you are talking about fries rather than chips / crisps is to add the adjective fritte (fried) after patatine.
Ho ordinato un contorno di patatine fritte al ristorante.
I ordered a side of fries at the restaurant.
Un sacchetto di patatine costa un euro e cinquanta centesimi.
A bag of chips costs one euro and fifty cents.
Patatina or la mia patatina (my little potato) is also a popular pet name (vezzeggiativo) Italian men call their wives and girlfriends. Just be extra careful not to inadvertently offend your beloved since it can also mean plump little girl!
Note: Patatina and the male equivalent pisello (which also means pea) are the terms that parents and teachers often use when talking to children about their private parts, so as to avoid the embarrassment of using the actual terms vagina (vagina) and pene (penis). Adults may also use the word patata in a jocular context as well, but be careful because people other than friends could consider it a bit vulgar.