On the word DINNER

古时候dinner是早餐的意思，后来演变成了午餐，现在指晚餐，成了supper的代名词。根据语境，有时候指正式晚宴，但是现在绝对不会有人用它来指午餐。

《牛津简明英语词典》（第九版）
dinner
1 the main meal of the day, taken either at midday or in the evening.
2 a formal evening meal, often in honour of a person or event.