A very interesting question: the --ed ending IS one of the signs to tell us that a word is a verb. ) From the examples you give, we can have "the work" (which would be a noun) and "the flow" ( which would also be a noun) We can only decide which way to label a word when we can see what it is "doing" in any particular sentence. In a way you are looking at it back to front, you do not need to learn a list of verbs and nouns, but if you DO want to label a word as a verb or a noun you have to look at it in context.
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