Omelettes

In cuisine, an omelette or omelet is a dish made from beaten eggs, fried with butter or oil in a frying pan. It is quite common for the omelette to be folded around fillings such as chives, vegetables, mushrooms, meat, or some combination of the above.

What is the difference between omelettes and frittatas?
Omelettes and frittatas are eaten not only for breakfast, but also as a main dish. 

In the strictest sense, the difference boils down to a matter of folding in a filling rather than mixing it in. Omelets traditionally have the egg mixture cooked and folded around a filling, while a frittata just mixes it all up, cooked in a mishmash combination all at once. Frittatas are often served at room temperature, making them perfect for brunches or larger groups.

Is it omelet and or omelettes?
Omelette is British and Canadian, while omelet is American.