Subject-Verb Agreement errors are among the most frequently tested error types in GMAT sentence correction. An understanding of the underlying grammar concepts helps us identify the errors quickly and also allows us to rectify them appropriately.

There are 6 basic rules that we need to understand in this topic. Let us look at them below.

1. Sentences that use Either - Or or Neither - Nor constructions

In sentences that use the above idiomatic constructions, we are likely to see two potential subjects that can influence the choice of verb.

For instance, in the sentence:

Either the main course or the desserts is are priced highly.  

We have to choose the verb based on the noun that is closest to it. This is the general rule to be followed in such cases. Here, 'desserts' is a plural noun, hence the verb should be plural as well.

Another example:

Either his sons or his daughter is are responsible for this.  

Here, the noun closest to the verb is 'daughter', which is a singular noun. Hence the verb should be singular as well.

2. Sentences that use Either or Neither (without Or or Nor)

When Either or Neither appear before the subject of the verb, we always use the singular verb.

For instance, in the sentence:

Either of the two dresses is are fine.  

We choose the singular verb 'is' even though we are talking about 'two dresses'. This is because we are referring to just one of them, not both of them.

Another example:

Neither of these fits fit me. 

Here again, we are referring to more than one object, but one at a time.

3. Sentences that use Each or Every

When the words Each or Every appear before the noun, the verb has to be singular.

For instance, in the sentence:

Each of the students has have to submit the homework.  

We choose the singular verb 'has' even though we are talking about 'students'. This is because we are referring to each one of them individually, not to all of them at once.

Another example:

Every minister and government officer was were vaccinated in the first round.  

Here again, even though we are talking about X and Y, we are saying that Every X was vaccinated and Every Y was vaccinated. Hence the singular verb has to be used.

4. Sentences that use an Additive

Consider the following sentence:

My niece Benafsh, who secured admission to Harvard's MBA program last year, is are arriving today.  

Here, the subject of the verb is Benafsh, hence the verb must take the singular form. The portion between the two commas, i.e.  who secured admission to Harvard's MBA program last year provides additional information about Benafsh, but is not the subject that the verb is referring to. Hence while matching the verb with its subject, this portion can be ignored.

Another example:

The bakery owner, alongwith his employees, is are visiting the NGO on Sunday.

Here, the subject of the verb is the bakery owner, hence the verb must take the singular form. The portion between the two commas, i.e.  alongwith his employees provides additional information about whom he/she is taking along, but is not the subject that the verb is referring to. Hence while matching the verb with its subject, this portion can be ignored.

5. Use of prepositions such as 'of', 'in' 'on' as part of the subject

Consider the following sentence:

The advantage of winning all the matches is are that the team qualifies directly for the finals.

Here, in the portion advantage of winning all the matches it is the 'advantage' that we are talking about. What the advantage is about (i.e. of winning all the matches) doesn't influence the verb. Since 'advantage' is singular, the verb must be singular.

Another example:

The guests in the auditorium is are asking for the air-conditioning to be switched on.

Here, in the portion guests in the auditorium it is the 'guests' that we are talking about. Where the guests are (i.e. in the auditorium) does not matter as far as the choice of verb is concerned. Since 'guests' is plural, the verb must be plural. 

6. Use of (modal) auxilliary verbs such as 'would', 'could', 'may', 'might', etc.

Consider the following sentence:

The cyclist might, subject to weather conditions, goes go for a short ride in the countryside.

The subject out here is 'cyclist' which is Singular. However, the verb used is 'go', which is plural. This is because there is an auxilliary verb 'might' before the verb 'to go'. We cannot say 'might goes', irrespective of the subject. We always have to say 'might go'. Hence the plural form (which is also the base form) of the verb is correct.

Another example:

Sheila said that she could feels feel the pain that her friend was going through.

The subject out here is 'Sheila' which is Singular. However, the verb used is 'feel', which is plural. This is because there is an auxilliary verb 'could' before the verb 'to feel'. We cannot say 'could feels', irrespective of whether the subject is singular or plural. Hence the plural form of the verb is correct.

7. Use of the Past Tense and Future tense in sentences

When the sentence is in the Past Tense, we do not need to worry about subject - verb agreement issues because the verb is the same for both singular and plural subjects.

For instance, we can say:

Yesterday, the student went home early.

Yesterday, the students went home early.

In both cases, we use 'went', which is the past tense of the verb 'to go'. There is no such verb as 'wents'

The only exception here is the verb 'to be', where we have to use 'was' for singular and 'were' for plural

For example:

The worksheet was difficult to solve.

The worksheets were difficult to solve.

In the Future Tense, we have to use the same rule as for the modal auxilliary verbs.

For example:

Chetan will goes go to the market after his class ends.

Even though the proper noun 'Chetan' is singular, we use the plural verb 'go' instead of 'goes'. After 'will', we have to use the base form of the verb.