雲が空を流れて行く。

cloud

indicates sentence subject (occasionally object); indicates possessive (esp. in literary expressions); but; however; still; and

sky; the heavens

indicates direct object of action; indicates subject of causative expression; indicates an area traversed; indicates time (period) over which action takes place; indicates point of departure or separation of action; indicates object of desire, like, hate, etc.

to stream; to flow (liquid, time, etc.); to run (ink); to be washed away; to be carried; to drift; to float (e.g. clouds); to wander; to stray; to sweep (e.g. rumour, fire); to spread; to circulate; to be heard (e.g. music); to be played; to lapse (e.g. into indolence, despair); to pass; to elapse; to be transmitted; to be called off; to be forfeited; to disappear; to be removed