Lunch is usually a smaller meal. Most people only
have an hour for their lunch, and they eat
sandwiches or 'takeaway' meal. Sometimes it is
the main meal of the day, and it is called dinner.
6 pm - 8 pm
dinner, tea, supper,
the evening meal
All these words are used for this meal.
Usually it is the most important meal of the day,
and if it is, it's called dinner.