This is the 120th most frequent Turkish word.
bütün
Whole; entire; all.
Here, 'bütün' is used to mean 'entire' or 'whole', emphasizing the completeness of the time period described.
Bütün gün ders çalıştım.
I studied the whole day.
Used to mean 'all' or 'every one of' in this sentence, 'bütün' emphasizes the entirety.
Bütün arkadaşlarım tatile gitmiş.
All my friends have gone on vacation.
In this example, 'bütün' is used to convey 'every part of', indicating inclusivity across the entire referenced object.