Isn't the following sentence grammatically correct?
The group of fifty people are going to arrive Thursday.
What's wrong with it? Someone said it should be
The group of fifty people is going to arrive Thursday.
Why? People is plural so why is people is better than people are?
Strictly speaking, the subject of the verb here is the singular noun group; of fifty people is just a prepositional phrase modifying the noun. It is parsed as if it were written thus:
The group (of fifty people) is going to arrive Tuesday.
It's not that simple, however. For one thing, group is a collective noun, which may be construed as either a singular or a plural, depending on your emphasis.
This group is larger than that group. Here you are contrasting two groups as undivided wholes.
This group are all children. Here you are characterizing the members of the group.
So which verb you use really depends on what you mean; and that's something that can’t be judged from this little fragment of discourse. Including the phrase of fifty people might mean you are trying to emphasize the count:
There are fifty people, in a group, who are going to arrive on Tuesday.
On the other hand, the phrase may be parenthetical, just thrown in for additional information:
The group, which has fifty people, is going to arrive Tuesday.
Or the phrase may be restrictive:
The group of forty people is going to arrive Sunday; the group of fifty people is going to arrive Tuesday.
Say what you mean, and in this case at least you’ll be OK. As the great linguist H.Dumpty said, “Take care of the sense and the sounds will take care of themselves.”
[NOTE: Speakers of British English are more likely to use the plural than speakers of American English. But both populations will understand you perfectly well, and hardly anybody will even notice which verb you use. Or care.]
The subject of the sentence is group, not people. The subject is people in the following sentence.
Fifty people are going to arrive Thursday.
Group is regarded as singular, so the verb should be declined for the third person singular, not for the third person plural.
Don't get confused from the word immediately preceding the verb; that word could be plural, but the subject be singular. For example, consider the following sentence:
One of my cousins visits the USA more often than I do.
The subject of the sentence is one of my cousins, a single person, and the verb must be declined as third singular person.
Keep in mind that, for example, news is generally regarded as singular, and neither of us is singular. The correct sentences would be then
The news is terrible.
Neither of us has seen your cousin.
