When a subject has two or more items joinedby and, we usually use a plural verb.But...
Plural subjects that function as a singleunit take a singular verb.A compound subject joined by and isplural and must have a plural verb.
When I is one of the two subjects connectedby either/or or neither/nor, put it secondand follow it with the singular verb am.
If one subject is singular and one plural andare connected by the words or, nor,neither/nor, either/or, and not only/butalso, the verb will agree with the nearestsubject.
Hard-to-find subjects.Some subjects can be harder to find thanothers. Subjects that come after the verb areespecially tricky.
Ignore intervening phrases.Disregard words or phrases that comebetween the subject and the verb. It is thesubject that determines whether verb issingular or plural and the subject is main noun,not a prepositional phrase.
When the pronoun who, that, or which isthe subject of a verb in the middle of thesentence. The pronouns who, that, andwhich become singular or plural accordingto the noun directly in front of them.
Sometimes the subject is separated from theverb by words such as along with, as well as,besides, or not. Ignore these expressionswhen determining whether to use a singular orplural verb.
When the subject is a gerund, an infinitive or a clause…
Words that indicate portions— percent,fraction, part, majority, some, all, none,remainder, and so on.
A collective noun can take either asingular or a plural verb.
Subjects that are singular in meaning but plural in form require a singular verb.1. Fields of study that end in –ics2. Certain illnesses that end in –s3. Arithmetic expressions4. Games5. Names and titles of movies, books etc.6. Expressions of time, money, and distance7. The word news.
References1. Betty Schrampfer Azar, Understanding and Using English Grammar, III Edition, Chapter 62. Martin Hewings, Advanced Grammar in Use, II Edition, Units: 40, 41, 423. George Yule, Oxford Practice Grammar (Advanced), Unit 14. Jane Straus, The Blue Book of Grammar and Punctuation, Grammar, Subject-Verb Agreement5. Laurie Rozakis, English Grammar for the Utterly Confused, Chapter 56. Loai Breigheith, English Language Grammar , Form and Function, Characteristics of the Subject7. Louis George Alexander, Longman English Grammar, Quantity, Distributives8. John Eastwood, Oxford Practice Grammar, II Edition, Unit 79, Agreement9. Sidney Greenbaum, The Oxford English Grammar, Unit 5, The Grammar of Phrases