Summary: Subject Verb Agreement

• Subject

Subject is the person/people/thing(s) that do the activity.
Example : I, you, they, we, she, he, it, my dad and my mom, Linda and Susi, the bank, the flight schedule, etc.

• Verb

Verb is a word used to describe an action, state, or occurrence, and forming the main part of the predicate of a sentence.

Kinds of verb :

• Action Verb

Also known as MAIN VERB.
Action verbs are words that express action (give, eat, walk, etc.) or possession (have, own, etc.). 
Action verbs can be either transitive (with object) or intransitive (without object). 
Example : Laurissa rises slowly from her seat.

• Linking Verb

A linking verb connects the subject of a sentence to a noun or adjective that renames or describes the subject.
To be : is, am, are, was, were.

Example : We were there!

Verb: seem, appear, become, grow, remain, get, prove, turn, look, sound, smell, taste, feel.

Example : That sounds great!

• Helping Verb

Helping verbs are used before action or linking verbs to convey additional information regarding aspects of possibility (can, could, etc.) or time (was, did, has, etc.) 

Modals always function as Helping Verbs.

Modals = can, could, may, might, shall, will, ought to, should, would.

Example : The trip might (helping verb) be (main verb) dangerous.

• MAIN RULE OF "Subject Verb Agreement"

Rule 1 : Subjects and verbs must agree in number.

Rule 2 : The words that come between the subject and verb; they do not affect agreement.

 
Rule 3 : Prepositional phrases between the subject and verb usually do not affect agreement.

Rule 4 : When sentences start with “there” or “here,” the subject will always be placed after the verb, so care needs to be taken to identify it correctly. 

Rule 5 : If two subjects are joined by and, they typically require a plural verb form. 

Rule 6 : The verb is singular if the two subjects separated by and refer to the same person or thing.

Rule 7 : If one of the words each, every, or no comes before the subject, the verb is singular.

Rule 8 : If the subjects are both singular and are connected by the words or, nor, neither/nor, either/or, and not only/but also the verb is singular. 

Rule 9 : The only time when the object of the preposition decides plural or singular verb forms is when noun and pronoun subjects like some, half, none, more, all, etc. are followed by a prepositional phrase. In these sentences, the object of the preposition determines the form of the verb. 

Rule 10 : The singular verb form is usually used for units of measurement or time. 

Rule 11 : If the subjects are both plural and are connected by the words or, nor, neither/nor, either/or, and not only/but also, the verb is plural. 

Rule 12 : If one subject is singular and one plural and the words are connected by the words or, nor, neither/nor, either/or, and not only/but also, you use the verb form of the subject that is nearest the verb. 

Rule 13 : Indefinite pronouns (everything, anything, everyone, someone, somebody, nothing, etc) typically take singular verbs. 

Rule 14 :Except for the pronouns (few, many, several, both, all, some) that always take the plural form.

Rule 15 : If two infinitives are separated by and they take the plural form of the verb. 

Rule 16 : When gerunds are used as the subject of a sentence, they take the singular verb form of the verb; but, when they are linked by and, they take the plural form.

Rule 17 : Collective nouns like family, committee, herd, senate, class, crowd, etc. usually take a singular verb form.

Rule 18 : Titles of books, movies, novels, etc. are treated as singular and take a singular verb.