I used to think that the word "dinner" has the same meaning as "supper". Actually if you look up these two words in many English-Chinese dictionary (you can try an online one such as dict.cn), you will find that "supper" means "a meal eaten in evening" while "dinner" means "a meal eaten in the evening", comma (or semicolon), "the main meal" (these are literally translated from the Chinese explanations). In China the main meal is always in the evening, hence I can't tell the difference between "a meal eaten in evening" and "the main meal".
One day, (by saying "one day" I really mean today), I happened to be curious (and bored) enough to do a google search for the difference between "dinner" and "supper".
Here're the results:
From the wiki page of "dinner"
In the United Kingdom, dinner traditionally meant the main meal of the day. Because of differences in custom as to when this meal was taken, dinner might mean the evening meal (typically used by people in the South) or the midday meal
In some regions, such as the southern or rural mid-western United States, the Atlantic Provinces, parts of Saskatchewan, and Quebec, the evening repast is called supper (souper in Quebec), and dinner (dîner) refers to the noon repast, which itself would be called lunch in most parts of the United States and Canada. In the Southern United States, the main repast of the day is called Dinner, whether taken at noon or in the evening. On farms it was traditionally taken at noon. If Dinner, the main repast of the day, is at noon, the evening repast is called Supper. If Dinner, the main repast of the day, is in the evening the noon repast is called Lunch.
From the wiki page of "supper"
In parts of North America, and the United Kingdom, dinner may be referred to as supper. In most of the United States and Canada, Supper and Dinner are considered synonyms
So it's quite regional (and confusing for those travelers, I guess).
By the way wikipedia lists many meal names in this section therefore you can check it in case you want to know "what the fuck should I call the meal I take at 11?"
But what makes the difference? Please welcome the history section. "What Time is Dinner?" by Sherrie McMillan gives a general picture about the change of mealtimes from Medieval Ages to modern days for different classes and region. (As you grow up, you will find that industrial revolution affects far more things than you can imagine.)
Bonus: Ever notice that the url of "What Time is Dinner" is http://www.history-magazine.com/dinner2.html instead of http://www.history-magazine.com/dinner.html ? You will find a menu for dinner in 1860 if you use the latter one.
