Verbs, or "action words," are among the most troublesome words in English.  Verbs come in a variety of types and change more than any other kind of word, depending on such things as tense, mood, and person.  Students frequently make mistakes in their handling of verbs, but knowing how verbs change can help you prevent many of those errors.

Split infinitives
Tense and Participles
Subject-verb agreement


The infinitive is the basic form of a verb.  It's called "infinitive" because it is the form a verb has before it has been "limited" by things like tense.  In English, the infinitive can be identified by the word "to":

    to run, to jump, to read

At one time, grammarians were quite firm in declaring that one should never "split" an infinitive.  Splitting an infinitive means putting an adverb between the "to" and the verb itself.  The most famous split infinitive (especially in science fiction) is:

     to boldly go where no man has gone before... ("to go" is the infinitive split by the adverb "boldly")

The rule was established because in other languages, particularly Latin, the infinitive is a single word, so it was thought that the English infinitive should be similarly treated as a unit.  Now, however, we say that you should avoid splitting the infinitive if you can, but go ahead and split it if the sentence would be very awkward otherwise, or if there's no way to avoid doing so:

    the company decided to more than double production.

Here, there is nowhere else to put the adverb "more than"; thus, splitting the infinitive "to double" is okay.

Transitive vs. Intransitive

A verb is said to be transitive if it takes an object--in other words, if the action is performed on something else; it is intransitive if it does not.  Most verbs can be either depending on the context; for example, "I ran" is intransitive because the action is not being done to anything else, but "I ran the race" does have an object.  Two words look and sound alike but are quite different: "to lie" is intransitive but "to lay" is transitive.  Be sure to use the correct forms:

To lie (e.g., on the bed)
To lay (e.g., carpet)
I lie
You lie
He/She/It lies
We lie
They lie
I lay
You lay
He/She/It lays
We lay
They lay
I lay
You lay
He/She/It lay
We lay
They lay
I laid
You laid
He/She/It laid
We laid
They laid
Past Participle
I have lain
You have lain
He/She/It has lain
We have lain
They have lain
I have laid
You have laid
He/She/It has laid
We have laid
They have laid


There are three tenses, and two types of tense.  The three tenses are past, present, and future; the two types are simple and compound. 

A simple tense is formed by changing the verb in some way; for example, in the simple past tense, we add
"-ed" to the verb if it's regular. 

A compound tense is formed by using an auxiliary verb (in most cases, either "to be" or "to have") plus a special form of the verb known as a participle.  There are two kinds of participle: past and present..

  past participle: if the verb is regular, it is formed by adding "-ed" to the verb; if it's irregular, you can
       easily figure out what the past participle is by using the verb in the phrase, "I have...":

          I have gone
          I have spoken

   present particple: it is formed by adding "-ing" to the verb

: While there is a simple past and a simple present, there really is no simple future in English; the closest we come (and it's sometimes called "simple future") is to put "will" before the verb.

Here are some examples:

To Walk

Simple Tenses
Some Compound Tenses

Simple Past Past Continuous (past tense of "to be" plus present participle)
I walked
You walked
She walked
We walked
They walked
I was walking
You were walking
She was walking
We were walking
They were walking

Simple Present Present Continuous (present tense of "to be" plus present participle)
I walk
You walk
She walks
We walk
They walk
I am walking
You are walking
She is walking
We are walking
They are walking

"Simple" Future
Present Perfect (present tense of "to have" plus past participle)     
I will walk
You will walk
She will walk
We will walk
They will walk
I have walked
You have walked
She has walked
We have walked
They have walked

  Pluperfect (past tense of "to have" plus past participle)

I had walked
You had walked
She had walked
We had walked
They had walked

Perfect, by the way, means that an action is finished
Continuous (or imperfect, progressive, etc.) means an action is ongoing

Participles are known as verbals: that means that they're verbs, but can also perform other functions.  For example, they can be used as adjectives:

     the walking man (present participle as adjective)
     the walked dog (past participle as adjective)

The present participle can be used as a noun; when it's used that way, it's known as a gerund:

     walking is good exercise

Dangling participle:
The problem comes from the fact that a participle remains a verb, and if you're not careful it will take a subject you don't mean, or it will lack a subject but clearly seem to need one.  Generally, it will take the nearest noun as its subject if it can:

     Even while walking along the sidewalk, speeding cyclists can pose a danger.
     While running down the street, his eyes glanced left and right.

The writer means "while one is walking along the sidewalk," but the sentence says that the subject of "walking" is "cyclists."  As for the second sentence: what is running down the street?

     Being broken in three places, I used epoxy to fix the lamp.

The writer is inadvertently saying that he or she, not the "lamp," is broken in three places.

     Driving down the highway, there is always something to look at.

"There" cannot be a subject of anything, so "driving" has no subject. 

Check your essay for dangling participles and recast any sentence that contains one.  Either supply a subject, or make the present participle into a gerund:

     The lamp was broken in three places, and I used epoxy to fix it.
     Driving down the highway is a great way to see many sights.

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Subject-Verb Agreement

Agreement means that a subject and its verb have to match in person and number
There are three persons: first, second, and third; and there are two numbers: singular and plural.
First person refers to the self; in the plural, it refers to the self plus others
Second person refers to the one(s) being addressed
Third person refers to someone or to more than one person other than the self and the one being addressed

Here's a chart showing the verb "to be" in its various forms:

I am
You (as in one person) are
He/She/It is
We are
You (as in more than one person) are
They are

With "to be," the form of the verb changes quite a bit; with most verbs, however, the only change you see generally involves the third person singular:

I walk
You (as in one person) walk
He/She/It walks
We walk
You (as in more than one person) walk
They walk

Note the "s" in the third person singular.  Subject-verb agreement errors occur when the writer loses track of whether the third person subject is singular or plural.  It can happen when something intervenes between the subject and verb and is in a different number:

Increasing the number of students, professors, and programs contribute to the stress on the system.

Here, the writer has gotten confused about the subject of "contribute"; "Increasing" is singular, but some plural nouns intervene--"students," "professors," and especially "programs"--so he or she has made "contribute" plural.  Always be sure you know what the true subject of your verb is, and then determine whether it's singular or plural.

There are some special circumstances that lead to understandable confusion.  Let's say you have an "either...or" sentence with choices that are of different numbers--in other words, one is singular and the other is plural.  The verb agrees with the closest subject:

Either the students or the professor is responsible.
Either the professor or the students are responsible.

Also, "as well as" is not the same as "and" and doesn't make the subject plural:

The student as well as the professor is responsible.

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There are two voices: active and passive.  Generally speaking, the active voice is better:  In the active voice, the noun does the action; in the passive voice, the action is done by the noun.  The passive voice is more wordy and it's weaker:

     The image of fire is used by the author. (passive)
     The author uses the image of fire. (active)

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