This is the 360th most frequent Japanese word.
東
East.
Here, "東" (east) specifies the direction of the sky that is described.
東の空が明るくなってきた。
The eastern sky has started to brighten.
In this case, "東" is used as an adjective to describe the region (eastern countries).
彼は東の国々を旅行したいと思っている。
He wishes to travel to eastern countries.
Here, "東" defines the cardinal direction guiding the movement.