A collective noun is one that names more than 1 person, place, or thing. When the group is regarded as a unit, the singular verb is the appropriate choice (see 9.2, Collective Nouns).
The couple has a practice in rural Montana. [Couple is considered a unit here and so takes the singular verb.]...
When 2 words or 2 groups of words, usually joined by and or or, are the subject of the sentence, either the singular or plural verb form may be appropriate, depending on whether the words joined are singular or plural and on the connector used....
When every or many a is used before a word or series of words, use the singular verb form.
Many a clinician does not understand statistics. (Better: Many clinicians do not understand statistics.)
Every issue profiles a leader in medicine.
Some nouns, by virtue of ending in a “plural” -s form, are mistakenly taken to be plurals even though they should be treated as singular and take a singular verb (eg, genetics, mathematics, measles, mumps, statistics) (see 9.9, False Singulars).
Genetics includes the study of heredity and variation of inherited characteristics....
A few plural nouns are used so often in the singular that they are often paired with a singular verb.
The agenda has been set for our next meeting.
Frequently treated erroneously in this way are the plurals bacteria, criteria, phenomena, and memoranda. The distinction between singular and plural, however, should be retained; when the singular is intended, use ...
Plural nouns take plural verbs and singular nouns take singular verbs, even if a phrase ending in a plural noun follows a singular subject or if a phrase ending in a singular noun follows a plural subject.
A review of all patients with grade 3 tumors was undertaken in the university hospital. [The subject in this sentence is ...
The number is singular and a number of is plural (see 7.5.5, Collective Nouns).
The number that responded was surprising.
A number of respondents were concerned about adverse effects.
The same is true for the total and a total of.
In clauses that follow one of those, either the plural or singular may be correct.
Dr Cotter is one of those researchers who prefer the library to the laboratory.
The nurse is one of those people who work tirelessly for others.
Unless one of those forms is completed, she cannot join the practice....
When -s or -es is added parenthetically to a word to express the possibility of a plural, the verb should be singular. However, in most instances it is preferable to avoid this construction and use the plural noun instead.
Elliptical constructions involve omission of the auxiliary verb because it is understood.
Her cholesterol levels were measured and her vital signs recorded.
The patient was examined and admitted.
This construction should not be used (ie, the auxiliary verb should not be omitted) if the number of the subject changes....
A predicate noun is the complement of a subject; it identifies, describes, or renames the subject. When the subject and predicate noun differ in number, follow the number of the subject in selecting the singular or plural verb form.
Avoid this by rephrasing:
Study results were most affected by interhospital variations in severity of illness....
The subject and verb must agree in number; use a singular subject with a singular verb and a plural subject with a plural verb. Unfortunately, this rule is often broken, especially in complex sentences.
Plural nouns take plural verbs and singular nouns take singular verbs, even if a phrase ending in a plural noun follows a singular subject or if a phrase ending in a singular noun follows a plural subject....