Subject verb Agreement . 

1. Single  subject takes single verb and plural subject takes plural verb.

Example :(i) Rama reads a book. (ii)They call the police. 

(iii) Romania and Zill reads the books .(  Incorrect)

   

  Romania and Zill read the books.( Correct )

2. If two singular Nouns refer to the same person or thing , the verb must be singular.

 

 Example : The Headmaster and  secretary is coming .

3. If the singular subjects are  preceded by every or each , the verb is usually singular.

Example: Every girl and boy ready .

4. Two or more singular subjects connected by or,nor,either,.....or neither.....nor take a verb in the singular.

Example:Neither he nor I was there.

5. When the subjects joined by or / nor are of different numbers , the verb must be plural ,and the plural subject must be placed next to the verb .

Example : Neither the principle nor the Assistant Headmaster were present.

6. When the subjects by or , nor are  of different persons the verb agrees in person with the one nearest to it .

Example : Either he or I am mistaken .

7. A collective noun takes a singular verb when the collection is thought of as a whole , a plural verb when the individuals of which it is composed are thought of .

Example: The council has chosen the president.

8. some nouns which are singular in form but plural in meaning , take a plural verb .

Example : Mathematics is a branch of study in every school . 

9. Words joined to a singular  subject by with , together with , in addition to , or as well as, etc . are parenthetical , and therefore do not affect the number of the verb 

Example : The chief , with all his men was massacred .

10. When the subject of the verb is relative pronoun care should be taken to see that the verb agrees in number and person with the Antecedent of the relative .

Example : I ,who am your friend will guard your in interests