Correct the sentence:
The ebb and flow of the tides / are / now understood.
In the above sentence I can go by two ways:
- First is that according to are I should be using the before flow thus making ebb and flow as the two different entities.
- Second is that since it is given as The ebb and flow , I can consider it as a single entity and use is in place of are.
Or is it that since tides is given , I need to go with are.
I'm quite confused. Suggestions please.
Best Answer
I'll introduce some jargon. The ebb and flow is a compound subject that uses the coordinating conjunction and. Compound subjects joined by and are usually treated as plural and consequently need a plural verb:
However, if the compound subject represents a single idea or a person, it is treated as a unit and a singular verb is used with it:
"The ebb and flow (of something)" can clearly be treated as a single unit:
And the same phrase has been sometimes treated as a combination of units in literature:
However, these quotes, or some of them, could serve as examples of deviation from the predominant perception of "ebb and flow" as a single unit, or even slight errors. Wait for native speakers' opinions.
My guess is that it's up to the author. If they want to stress the wholeness of the subject, they might use a singular verb, or they might use a plural in order to stress the distinctness of "ebb" and "flow".