This is the 1166th most frequent Japanese word.
平日
Weekday.
Here, '平日' refers to regular weekdays when schools and offices are typically operating, distinguishing those days from weekends.
平日は学校があります。
On weekdays, there is school.
In this sentence, '平日' is used to specify a menu that is offered exclusively on weekdays, indicating the limited availability based on the day.
平日限定メニューがあります。
There is a weekday-only menu.
The word '平日' is contrasted with '週末' (weekend), highlighting the thematic comparison between regular weekdays and weekends regarding activities.