Downstream means with the flow of a river. Float downstream, a mile downstream, downstream of the bridge.
It names direction and position both. Figuratively it means later in a process — downstream effects are the ones that show up further along, and in the oil industry downstream means refining and selling as against extraction. Note upstream, its exact opposite; and that pollution problems are always felt downstream.
1adverbdownstreamWith the flow of a river.
“The boat drifted downstream until it reached the old stone bridge.”
2adjectivelaterLater in a process.
“Errors in the data cause downstream problems for every team that uses it.”
downstream is a direction.
Middle English
doun
English
down
English, today
downstream
Built from
From down- + stream. down comes from Middle English doun. From Middle English doun, doune (“down”), from Old English dūne (“down”), aphetic form of adūne (“down, downward”), from earlier ofdūne (“down”) literally “off the hill”, from of (“of, off of”) + dūn (“hill, mount, dune, down”). More at Etymology 2 below. For the development from directional phrases to prepositions, compare dene, dāle, whence dal. Compare also stq, del. Cognate with Scots doon (“down”).
Etymology from Wiktionary, CC BY-SA