Subject-Verb Agreement

Basic English grammar states that every singular subject must be followed by a singular verb. Every plural subject must be followed by a plural verb. However, the words will try to trick you by placing many different nouns before a sentence’s main verb, hiding a sentence’s main subject. Therefore, whenever you see a sentence correction problem, your first objective should be to identify the subject of a sentence.

In this lesson you will be tested on your ability to use correctly the forms of the verb be (is, are, was and were) and the verb have (has and have).

The verb is is used with a singular subject. The verb are is used with a plural subject.

Examples:

1. Mr. Subali is in Jakarta. (He is in Jakarta.)
2. The motorcycle are in the garage. (They are in the garage.)

The word was is used with a singular subject. The word were is used with a plural subject.

Examples:

1. The tea was cold. (It was cold.)
2. The visitor were late. (They were late.)

The word has is used with a singular subject. The word have is used with a plural subject.

Examples:

1. Mariska has a cold. (She has a cold.)
2. The Haris have two children. (They have two children.)

When the word you is the subject of the sentence, the plural form of the verb is used, even if the word you refers to only one person.

Examples:

1. You are late. (Do not use is.)
2. You were late. (Do not use was.)
3. You have done a good job. (Do not use has.)

In the present tense the third person singular form of a verb (he, she or it) always ends in an s.

In each sentence in the first two lessons, the verb had only one subject.

Example:

1. Her parents like living in Tobalake. (The subject of the verb like is parents.)

These sentences will contain more than one subject.

Example:

1. Rudy and Aelke like to visit Tobalake. (The subjects of the verb like are the words Rudy and Aelke.)

When a verb has more than one subject, the subjects are joined by the word and or the word or.

Examples:

1. Susi and Risman are in the waiting room.
2. Susi or Risman is in the waiting room.

Two or more singular subjects joined by the word and require a plural verb.

Example:

1. John and Sam walk to work every morning. (Both of them walk.)

Two or more singular subjects joined by the word or require a singular verb.

Example:

1. John or Sam walks with me to the college every morning. (Only one of them walks.)

Two or more plural subjects require a plural verb, no matter which word is used to join the subjects.

Examples:

1. My sons and my daughters wash the dishes after supper.
2. My sons or my daughters wash the dishes after supper.

Courtesy :

http://www.tcdsb.org/section23/grammar/subjectva.htm#

http://www.thegmatbootcamp.com/sentence-correction/subject-verb-agreement/