One example. Casserole.
Here's the French definition :
1. Ustensile de cuisine de forme cylindrique, à manche ; son contenu.
2. FAMILIER Mauvais piano.
It means a saucepan with a handle. You can get a batterie de casseroles, but let's not get too ambitious.
I grew up in South Wales in an English-speaking household. From time to time my mother would cook a casserole, which was a kind of stew, but cooked slowly in the oven typically in a "Pyrex" oven-proof glass dish often referred to as a Pyrex Casserole.You could make chicken casserole or beef casserole and you'd know what you'd get. You could buy a set of Pyrex casseroles for a wedding present so people would start their married life with a matching set in different sizes.
American friends understand something completely different by the word casserole. They make "green bean casserole" and I don't have any idea what that means at all.
Now that's just one word, but in our vocabulary we have many, many words, and as time goes on so my confusion grows.