Expressions like:
A number of
A lot of
A host of
Are plural and thus go with "are" form of to be, for example:
There are a number of clear contrasts.
but contrary to these, I usually see:
There is a vast array of clear contrasts.
And not:
There are a vast array of clear contrasts.
In sentences, is there any rationale behind it?
There are a number of clear contrasts.but contrary to this, I usually see:
There is a vast array of clear contrasts.Is there any rationale behind it?
Although the choice of singular or plural verb is ultimately up to the writer or speaker, I agree with you that your example sentences reflect what one usually sees and hears people writing and saying.
I can try to rationalize why these choices feel right to most people. "A lot of genres" and "numerous genres" hopefully need no explanation.
"A number of" feels to most people like those two do.
"My painting collection is in the moving truck" is not in a gray area. I think most people feel that "There is a vast collection of books on Churchill at the university library" is similar to the painting collection example. Next step, "There is a vast array of books on Churchill at the library." Final step, "There is a vast array of clear contrasts."
So, we're treating array of clear contrasts as a singular noun with a prepositional phrase.
If I didn't understand which aspect you'd like explained, please write a comment.
