This is the 98th most frequent French word.
vendredi
Friday.
The word 'vendredi' is used here to specify the day of the week when an event will occur.
Nous partirons en vacances vendredi.
We will leave for vacation on Friday.
In this sentence, 'vendredi' is used generically to refer to the recurring day of the week 'Friday' in a habitual context.
Le vendredi, il y a souvent moins de circulation.
On Fridays, there is often less traffic.
Here, 'vendredi' in the plural 'vendredis' emphasizes routine action happening every week on Friday.