Dinner used to be the name of the main meal of the day. Originally, it referred to the first meal of the day, eaten about noon, and is still occasionally used in this fashion if it refers to a large or main meal.
So whenever you eat dinner, keep in mind that eating well means enjoying a variety of food—and so does eating to stay well. Variety matters because no food has all the nutrients and other substances needed by your heart—and the rest of your body. So be sure to follow a well-balanced eating plan. It also means that previous meals influence what you will eat next: a big lunch shouldn’t be followed by a similar dinner!