The prevailing mood is one of optimism.

[kadioguy]

The prevailing mood is one of optimism.

https://dictionary.cambridge.org/zht/詞典/英語/optimism

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I don't know why there is a "one of" before the "optimism".

a. The prevailing mood is one of optimism.

b. The prevailing mood is optimism. (My original sentence)

I assume:

(a) means that there are different kinds of optimism, and the prevailing mood is one of them.

(b) tells us the same thing, but in a general way.

What do you think?

 

[Rover_KE]

Alternatively, and with the same meaning: The prevailing mood is optimism.

 

[Charlie Bernstein]

If I were getting rid of "one of," I'd probably say, "The prevailing mood is optimistic."

 

[tedmc]

It think the two extra words (one of) are added for style, to make the sentence longer and less direct, though it means the same thing.

 

[kadioguy]

I[STRIKE]t[/STRIKE] think the two extra words (one of) are added for style, to make the sentence longer and less direct, though it means the same thing.