River flows swiftly downstream.
Meaning: This sentence describes the rapid movement of water in a river as it flows downstream.
Choice of Words: River is a large natural stream of water. Flows is a verb that means to move or run in a continuous stream. Swiftly is an adverb that means quickly and without delay. Downstream is an adverb that means in the direction that a river flows. When you put them together, "River flows swiftly downstream" means that a river moves quickly in the direction that it flows.
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