This is the 83rd most frequent Indonesian word.
bulan
"Month" or "moon."
In this sentence, "bulan" refers to the celestial object, the Moon.
Bulan Sabit terlihat di langit malam.
The Crescent Moon can be seen in the night sky.
Here, "bulan" signifies a unit of time, specifically a month.
Kami akan berlibur selama satu bulan.
We will vacation for one month.
In this context, "Bulan" refers to the specific astronomical entity known as the Moon, with capitalization indicating a proper noun.