Breakfast; a meal eaten in the morning as the first meal of the day
Lunch: a meal that is eaten in the middle of the day
Dinner: the main meal of the day, usually the meal you eat in the evening
Of course, This practice varies from country to country. For example; in Britain, dinner is the meal eaten in the middle of the day.
We should have dinner together next week= You must take your meal with your friend either in the evening or at noon (according to prevailing practice of your country)