Actually, that's not quite right. I eat my main meal in the evening on weekdays, but on Saturday and Sunday when I'm home, we eat in the middle of the day.

Sunday lunch is still called that even though it's the main meal. The meal we have in the evening on those days is called "tea", though.

Supper is a snack you have later in the evening - I don't usually but Dad always has something around 9.30-10pm.

So lunch is lunch, but tea or dinner depends on what we are eating.