Agreement of the verb with the subject

Singular subjects take singular verbs

A verb must agree with its subject in number and person.

• He is my friend. (Here the singular verb is agrees with the singular subject he.)
• We are waiting to hear from you. (Here the plural verb are agrees with the plural subject we.)

Sometimes due to what is called ‘the error of proximity’ a verb is made to agree with the nearest noun, and not its proper subject. This practice should be avoided.
Consider the examples given below:

• The quality of the apples wasn’t very good. (NOT The quality of the apples weren’t very good. Here the proper subject is the abstract noun ‘quality’ and not ‘apples’.)
• His proficiency in Indian languages is remarkable. (Here the proper subject is the singular abstract noun ‘proficiency’ and not ‘languages’.)

as well as

We use singular verbs with a singular subject followed by ‘with’ or ‘as well as’.

• The manager, with his subordinates, is to be present at the venue. (NOT The manager with his subordinates are …)
• Alice, as well as her sisters, has been invited. (NOT Alice as well as her sisters have been invited.)
• Sanskrit, as well as Arabic, is taught here.

When one of the subjects joined by or or nor is plural, the verb must be plural in number, and the plural subject should be placed nearest to the verb.

• Neither the officer nor his subordinates were present at the meeting. 
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When the subjects joined by or or nor are of different persons, the verb agrees with the nearest noun.

• Either he or you are mistaken. (Here the verb are agrees with the nearest pronoun you.)
• Neither he nor I am interested. (Here the verb am agrees with the nearest pronoun I.)

It is better to avoid these constructions and to write:

• He is mistaken, or else you are.
• He is not interested, nor am I.

Either, neither etc.

Either, neither, each, everyone and many a must be followed by a singular verb.

• Neither of the applicants is suitable for the job.
• Many a man has succumbed to this temptation.
• Everyone of us loves riding.