SYNTAX (=CONCORD or AGREEMENT)
(a) A Number of is used for indefinite number --- Plural Verb (As Indefinite number is treated as Plural)
e.g. A number of students have come.
A number of children are playing.
(b) The Number of is used for Definite number ---Singular Verb (As definite number is treated as Singular)
e.g., The number of graduates is increasing.
The number of guests varies.
(c) Singular Verb is used with Quantitative Expressions. (Either Definite or Indefinite as Quantity is treated as Singular)
e.g., A lot of butter has been purchased
much of milk has turned sour.
A good deal of food is found to be tasteless.
Similar Numerical / Quantitative Expressions are: Many of, Half of, Some of, Much of, Most of, Majority of, Part of, Percent of, None of, All of, A few of, A handful of, All of, Rest of, A lot of, Lots of, Heap of, Plenty of, A great deal of, etc.
Rule 17: Many a/an + Singular Noun/ More than one; structured sentences have Verb in Singular Number because the form of the sentence is singular (Subject singular but meaning plural).
e.g., Many an opportunity is missed by negligence.
More than one chance was given to him.
Note: But if the structure of the sentence is changed as More + Plural Subject +Than one, then Plural Verb should be used.
e.g., More opportunities than one are missed by negligence.
More chances than one were given to him.
Rule 18: Singular Verb is used with expressions having structure
Singular Collective Noun + of + Plural Noun
e.g., A group of, A band of, A team of, A herd of, A flock of, A chain of, A class of, A set of, A bouquet of, A galaxy of, A fleet of, A pair of, A gang of, etc.
A garland of flowers is ready.
A batch of students is studying here.
In these cases the verb is used in accordance with Subject (A group of, A team of etc.) which is singular in nature.
Rule 19: Singular verb is used with Hyphenated Expressions/ Singular Noun Repeated after a Preposition. (Plural Noun cannot be used)
e.g., Wave after wave, Ship after ship, Mistake after mistake, Attempt after Attempt, Question after question Brick upon brick, Storey upon storey, Box into box, etc.
Question after question was asked to me.
Storey upon storey is being built.
Attempt after attempt was made.
Rule 20: As follows is always used in Singular Number. (As follow is never used)
e.g., The conditions are as follows.
The account of expenditure is follows.
The main points are as follows.
Rule 21: If two Subjects are connected by Not only…………but, then the verb in Its number and person is in accordance with the Second Subject. (Subject coming after But)
e.g., Not only the teacher but all his students are serious.
Not only his sons but he himself is a great dancer.
Rule 22: Singular Verb is used with the expressions having structure:
Nothing But + Noun Singular or Plural (Here Subject is Nothing But)
e.g., Nothing but smoke was there.
Nothing but hills is seen there.
Rule 23: Sentence beginning with ‘There’. Is / Are is used according to the subject following is/are.
e.g., There is a book on the table.
There are some books on the table.