A. In simple present tense :When the subject is third person singular, the verb must have the [-s] form, i.e. end with - s or -es.
- My friend lives in Boston. ('friend' is third person singular)
- The sun rises from the east. ('sun' is third person singular)
- The dress looks like a brand new. ('dress' is third person singular)
It is easier to remember to make the subject and the verb to agree when the verb comes immediately after the subject. However, many English learners fail to make the subject and the verb agree when they are separated by a prepositional phrase, a relative clause or an adverbial phrase:
- The mother of these boys work as a computer programmer.
(The verb 'work' is agreeing with 'boys', but 'boys' is the object of the prepositional phrase 'of these boys'. It should agree with the subject, 'mother', which is singular.)
- The mother of these boys works as a computer programmer.
- The clothes that I gave to my sister was too small for me.
(The verb 'was' is agreeing with 'sister', but 'sister' is part of the relative clause 'that I gave to my sister'. The subject of this sentence is 'clothes', which is plural.)
- The clothes that I have to my sister were too small for me.
- President George Bush, like most previous presidents, come from a wealthy family.
(The verb 'come' is agreeing with 'presidents', which is part of the adverbial phrase 'like most previous presidents'. In this sentence 'President George Bush' is the subject, with which the verb must agree.)
- President George Bush, like most previous presidents, comes from a wealthy family.
B. A gerund subject is always considered singular.
- Jogging is good for your health.
- Smiling causes people to be nicer.
C. With most phrases of quantity, the verb agrees with the noun in the phrase.
When the quantity is singular such as 'one of', 'each of', 'every one of', or 'a group of'', the verb is singular but the noun of that phrase must be plural.
- Each of the book costs $1.
- Each of the books costs $1.
- One of the room is very messy.
- One of the rooms is very messy.
- A group of student is touring the campus.
- A group of students is touring the campus.
D. With some nouns, it is not obvious that they are singular or plural.
1. Names of places or things are singular.
e.g. countries (the United States, the Netherlands), organizations (the United Nations).
2. 'News' is singular.
3. Fields of studies are singular.
e.g. economics, physics, mathematics, statistics.
4. Diseases or medical conditions are singular.
e.g. diabetes, measles, mumps, rabies, rickets, shingles.
5. Expressions of measurements (time, money, distance, weight) are singular.
e.g. three days, one hundred dollars, two miles, fifty pounds.
6. Arithmetic expressions use singular verbs.
7. Some nouns are plural even though they do not end with -s or -es.
e.g police, cattle, people, sheep, fish, staff, faculty.
8. Languages are singular, but a noun that means the people of a country takes a plural verb.
9. When an adjective is preceded by 'the', it means the people with that quality or characteristic (the poor = the poor peole, the rich = the rich people, the disabled = the disabled people) and it requires a plural noun.