According to Longman Dictionary, diner means 1- someone who is eating in (a restaurant) 2- a small restaurant that serves cheap meals (especially American English) Dinner means 1-the main meal of the day, eaten in the middle of the day or the evening. 2-a formal occasion when an evening meal is eaten, often to celebrate something.

Hi Elizabeth A diner is a person who dines - they eat a meal. It can also be a type of cafe. Dinner is a meal that you eat.

oops - cafe in English = small restaurant, not coffee!