This is the 5221st most frequent Chinese word.
上山
"Go up the mountain" or "Ascend the mountain."
In this sentence, '上山' is used as a verb that means 'to go up the mountain', indicating the action of ascending a mountain.
他们准备上山观看日出。
They are preparing to go up the mountain to watch the sunrise.
Here, '上山' is used as an adjective modifier to describe a road leading upward to the mountain.
这条上山的路非常陡。
This road up the mountain is very steep.
In this instance, '上山' functions again as a verb phrase describing the habitual action of ascending the mountain.