why do we use "of" here, this structure can be repeat after other verbs, but "to be"?

Question

In some sentence, we see that the "of" is used, do you think the use of it is need? for example:

1- It is of the utmost/highest importance,
2- those built were of interest,
3- cooperation should be of great value,
4- He’s a bigot of the highest order.

In the above example, we can see that the "of" is exercised between a Linking verb and an (superlative) adjective. Is there any specific role about the usage of "of", here?

this structure, i.e. "of" + "(superlative) adjective", can be used for other verbs, excluding "be"?

Answer 1

The "of" is not redundant in any of your sentences, because you can't remove it without changing the words.

Saying something is "of importance" is another way of saying it is important. You cannot say "of important", so your first example would have to change:

• It is of the utmost importance
• It is the most important.

The same goes for examples 2 and 3:

2. those built were of interest = those built were interesting
3. cooperation should be of great value = cooperation should be highly valuable

Your final example is slightly different in that "of the highest order" is idiomatically used as a suffix to add weight to something.

4. He’s a bigot of the highest order.

You could say "he's highly bigoted" which means the same, but doesn't carry quite the same impact. When used this way, it exaggerates it and makes it insulting.

Some similar examples are idiomatic one way or the other. For example "a person of colour" is considered to be a polite and acceptable term for someone who is not white, while the alternative "a coloured person" is considered to be insulting.

Answer 2

"of interest", "of (great/utmost/no/dubious...) importance" and similar are phrases that function as adjectives. "Interest", "importance" etc. are nouns.

When you say, "this thing has [something]," you're looking for a noun: "This thing has (great) value."

When you say, "this is a [such-and-such] thing," you're looking for an adjective: "This is a thing of (great) value."