Grasso vs. unto

The Italian words 'grasso' and 'unto' both relate to fatty or greasy qualities, but they have subtle differences in usage and connotation.

Grasso

'Grasso' primarily refers to fat content or a fatty state, often used to describe food or body composition.
Questo formaggio è molto grasso.
(This cheese is very fatty.)
Il maiale è considerato un tipo di carne grassa.
(Pork is considered a fatty type of meat.)
Ho comprato del latte intero perché è più grasso.
(I bought whole milk because it's fattier.)

Unto

'Unto' specifically describes something that is greasy or oily, often implying an excess of oil or grease on the surface.
Le mie mani sono unte dopo aver mangiato la pizza.
(My hands are greasy after eating pizza.)
Il piatto unto ha lasciato una macchia sulla tovaglia.
(The greasy plate left a stain on the tablecloth.)
La padella è unta e ha bisogno di essere lavata.
(The frying pan is greasy and needs to be washed.)

Summary

While 'grasso' generally refers to fat content or a fatty state, 'unto' specifically describes a greasy or oily surface or texture. 'Grasso' is more commonly used for describing food composition or body fat, whereas 'unto' is often used to describe the residue or feel of grease on objects or skin.