A complete sentence has a subject, has a predicate, and can stand on its own. A sentence fragment cannot stand on its own as a sentence because it lacks a subject, a predicate, or both, or for some other reason fails to convey a complete thought. Though common in ads and fiction, fragments are not usually effective in college writing because they do not express coherent thoughts.

To edit for fragments, check that each sentence has a subject and a verb and expresses a complete thought. To correct a fragment, complete it by adding a missing part, dropping an unnecessary subordinating conjunction, or joining it to a nearby sentence, if that would make more sense.

A complete sentence has a subject and a predicate and can stand on its own. When two sentences are combined as one sentence, each sentence within the larger one is called a main clause. However, writers need to follow the rules for joining main clauses to avoid serious sentence errors. A comma splice is two main clauses joined with only a comma. A fused sentence (or run-on) is two main clauses joined with no punctuation at all.

To find these errors, examine the main clauses in each sentence to make sure they are joined correctly. Correct a comma splice or fused sentence in one of these four ways, depending on which makes the best sense:

The form of a verb, the way it is spelled and pronounced, can change to show its tense — the time when its action did, does, or will occur (in the past, present, or future). A verb about something in the present will often have a different form than a verb about something in the past.

Regular verbs are verbs whose forms follow standard rules; they form the past tense by adding -ed or -d to the present tense form:

Check all regular verbs in the past tense for one of these endings.

TIP: If you say the final -d sound when you talk, you may find it easier to add the final -d or -ed when you write past tense regular verbs.

Because irregular verbs do not have standard forms, their unpredictable past tense forms must be memorized. In addition, the past tense may differ from the past participle. Check a dictionary for these forms.

TIP: In college papers, follow convention by using the present tense, not the past, to describe the work of an author or the events in a literary work.

The form of a verb, the way it is spelled and pronounced, can change to show number — whether the subject is singular (one) or plural (more than one). It can also show person — whether the subject is you or she, for example.

A verb must match (or agree with) its subject in terms of number and person. Regular verbs (whose forms follow a standard rule) are problems only in the present tense. There they have two forms: one that ends in -s or -es and one that does not. Only the subjects he, she, it, and singular nouns use the verb form that ends in -s or -es.

The verbs be and have are irregular, so their present tense forms must be memorized. The verb be is also irregular in the past tense.

Problems in agreement often occur when the subject is hard to find, is an indefinite pronoun, or is confusing. Make sure that you include any -s or -es endings and use the correct form for irregular verbs.

Depending on the role a pronoun plays in a sentence, it is said to be in the subjective case, objective case, or possessive case. Use the subjective case if the pronoun is the subject of a sentence, the subject of a subordinate clause, or a subject complement (after a linking verb). Use the objective case if the pronoun is a direct or indirect object of a verb or the object of a preposition. Use the possessive case to show possession.

Writers often use the subjective case when they should use the objective case — sometimes trying to sound formal and correct. Instead, choose the correct form based on a pronoun’s function in the sentence. If the sentence pairs a noun and a pronoun, try the sentence with the pronoun alone.

A second common error with pronoun case involves gerunds. Whenever you need a pronoun to modify a gerund, use the possessive case.

The form of a pronoun, the way it is spelled and pronounced, can change to show number — whether the subject is singular (one) or plural (more than one). It also can change to show gender — masculine or feminine, for example — or person: first (I, we), second (you), or third (he, she, it, they).

A pronoun refers to its antecedent, usually a specific noun or pronoun nearby. The connection between the two must be clear so that readers know what the pronoun means in the sentence. The two need to match (or agree) in number and gender.

A common error is using a plural pronoun to refer to a singular antecedent. This error often crops up when the antecedent is difficult to find, is an indefinite pronoun, or is confusing for another reason. First, find the antecedent, and decide whether it is singular or plural. Then make the pronoun match its antecedent.

Indefinite pronouns are troublesome antecedents when they are grammatically singular but create a plural image in the writer’s mind. Fortunately, most indefinite pronouns are always singular or always plural.

Adjectives and adverbs describe or give information about (modify) other words. Many adverbs are formed by adding -ly to adjectives: simple, simply; quiet, quietly. Because adjectives and adverbs resemble one another, writers sometimes mistakenly use one instead of the other. To edit, find the word that the adjective or adverb modifies. If that word is a noun or pronoun, use an adjective (to describe which or what kind). If that word is a verb, adjective, or another adverb, use an adverb (to describe how, when, where, or why).

Adjectives and adverbs with similar comparative and superlative forms can also cause trouble. Always ask whether you need an adjective or an adverb in the sentence, and then use the correct word.

Good is an adjective; it describes a noun or pronoun. Well is an adverb; it modifies or adds to a verb (heal, in this case) or an adjective.