© Damen, 2002
9. Subject-Verb Agreement.
If grammar is physics, then subject-verb agreement is Newton's First Law. It's fundamental and a very simple thing really, but so many students in my experience don't do it right I feel the need to comment on it here. This is it in a nutshell:
1. Certain subjects (the person or thing doing the action in a sentence) go with certain types of verbs.
2. For instance, a subject like "he/she/it" or the equivalent (called "third-person singular") requires a present-tense verb that ends in -s, for example: the student understands, she learns, it does.
3. Other forms which are not third-person singular take present-tense verbs that do not end in -s, for example: I have, they know, you learn.
This is true only of verbs in the present tense (i.e. when the action of the verb is happening at the present moment). Most other tenses don't employ the -s at all: she saw, he will see, Caesar used to see.* It's really very simple and should be automatic for most English-speakers: I read, you read, but he reads.
Compound Subjects. It's my experience that students most often fail to follow the rule of subject-verb agreement when a subject is compound (two separate subjects linked by a conjunction such as "and"): "You and Mark learn," "she and I are," "knowing, understanding and teaching represent different stages of learning." In this case, because there are two (or more) third-person singular nouns acting as the collective subject, the subject is plural—one and one make two—and thus the verb doesn't end in -s.
Even more complex subjects only make matters worse: "The various myths of creation found in different societies around the world and their similarity are intriguing." Here, the subject is compound—"myths" and "similarity"—and thus it is plural. So again, there is no -s on the verb.
Worse yet, this rule is reversed with the conjunction "or": "Julius Caesar or Augustus Caesar is said to be the first Roman emperor." Since it's either "Julius" or "Augustus," the subject is singular—one or one is still one—and thus there's an -s on the verb. When "or" joins a singular and a plural subject, the verb agrees with the one nearer to it: "The Senate or, later, the Senate and the tribunes are seen to have controlled Republican Rome, according to most Roman historians." Here the plural subject ("tribunes") is closer to the verb and so the verb is plural ("are"). If, in contrast, the singular subject is closer, the verb will agree with it: "The Senate and the tribunes or, earlier, the Senate alone is seen to have controlled Republican Rome, according to most Roman historians." The singular subject ("Senate") is closer to the verb which as a result is singular ("is").
All in all, it is vital you make sure the subjects and verbs of your sentences agree. Especially when you write more than a simple subject, check the agreement of the verb with the subject. Remember this will be a problem mainly with the present tense. Listen to your common sense. Most English speakers do this by nature correctly.
*Some irregular verbs, such as "to be" and "to have," have -s in their past-tense forms, but they are relatively few and should be automatic to native English speakers: she was, he has had (versus you were, they had).
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