Verbs - Grammar

AMA Manual of Style - Stacy L. Christiansen, Cheryl Iverson 2020


Verbs express an action, an occurrence, or a mode of being. They have voice, mood, number, and tense (see 7.5, Subject-Verb Agreement).

7.4.1 Voice.

In the active voice, the subject does the acting; in the passive voice, the subject is acted on. In general, authors should use the active voice, except in instances in which the actor is unknown or the interest focuses on what is acted on (as in the following example of passive voice).

A randomization list using variable blocks of 2, 4, or 6 was generated by an independent statistician. (Compare: An independent statistician generated a randomization list using variable blocks of 2, 4, or 6.)

If the actor is mentioned in the sentence, the active voice is preferred over the passive voice.


Data were collected from 5000 patients by physicians.


Physicians collected data from 5000 patients.


Baseline clinical features and a throat swab were obtained.


Study clinicians obtained baseline clinical features and a throat swab.


Maintenance therapy and the clinical status of patients were evaluated every 6 months.


We evaluated maintenance therapy and the clinical status of patients every 6 months.

7.4.2 Mood.

Verbs may have 1 of 3 moods: (1) the indicative (the most common; used for ordinary objective statements), (2) the imperative (used for requesting or commanding), and (3) the subjunctive.

Indicative verbs are used to state a fact, opinion, or question.

The surgeon entered the room.

I think the study has serious flaws.

Did you submit your paper?

Imperative verbs give direction or commands. They are often part of a “you understood” construction.

Bring that wheelchair over here.

Stop it.

Subjunctive verbs cause the most difficulty; they are used primarily for expressing a wish (I wish it were possible), a supposition (If I were to accept the position . . . ), or a condition that is uncertain or contrary to fact (If that were true . . . ; If I were younger . . . ). The subjunctive occurs in fairly formal situations and usually involves past (were) or present (be) forms.

Past form:

If we were to begin treatment immediately, the patient’s prognosis would be excellent.

Present form:

The patient insisted that she be treated immediately.

7.4.3 Tense.

Tense indicates the time relation of a verb: present (I am), past (I was), future (I will be), present perfect (I have been), past perfect (I had been), and future perfect (I will have been). It is important to choose the verb that expresses the time that is intended. It is equally important to maintain consistency of tense.

The present tense is used to express a general truth, a statement of fact, or something continuingly true.

He discovered enzymes—RNA polymerases—that directly copy [not copied] the messages encoded in DNA.

For this reason, the present tense is often used to refer to recently published work, indicating that it is still valid.

Kilgallen’s assay results demonstrate the highest recorded sensitivity and specificity to date.

The present perfect tense illustrates actions completed in the past but connected with the present1 or those still ongoing. It may be used to refer to a report published in the recent past that continues to have importance.

Kaplan and Rose have described this phenomenon.

The past tense refers to a completed action. In a biomedical article the past tense is usually used to refer to the methods and results of the study being described:

We measured each patient’s blood pressure.

Group 1 had a seropositivity rate of 50%.

The past tense is also used to refer to an article published months or years ago that is now primarily of historical value. Frequently a date will be used in such a reference.

In their 1985 article, Northrup and Miller reported a high rate of mortality among children younger than 5 years.

In general, tense must be used consistently:


There were no adverse events reported in the control group, but there are 3 in the intervention group.


There were no adverse events reported in the control group, but there were 3 in the intervention group.

However, tense may vary within a single sentence, as dictated by context and judgment. For example, the past tense and the present tense may be used in the same sentence to place 2 things in temporal context:

We determined which medications are used most frequently by this population.

Although the previous report demonstrated a significant response, the follow-up study does not.

Even when tenses are mixed, however, consistency is still the rule:


I found it difficult to accept Dr Smith’s contention in chapter 3 that the new agonist has superior pharmacokinetic properties and was therefore more widely used.


I found it difficult to accept Dr Smith’s contention in chapter 3 that the new agonist has superior pharmacokinetic properties and is therefore more widely used.

7.4.4 Double Negatives.

Two negatives used together in a sentence constitute a double negative. The use of a double negative to express a positive is acceptable, although it yields a weaker affirmative than the simpler positive and may be confusing:

Our results are not inconsistent with the prior hypothesis.

More direct incentives have produced substantial changes in behavior in the past, although not without adverse consequences.

Adverse effects were not uncommon in both groups.

However, it is not grammatically acceptable to use a double negative to emphasize the negative. In the following example, the double negative conveys the opposite of what is intended.

The results are not inconclusive.

A double negative is best avoided in scientific writing because it often causes the reader to go back and reread the sentence to make sure of the meaning.

7.4.5 Split Infinitives and Verb Phrases.

Infinitives are the basic form of verbs. In English, they are always a 2-word construction that starts with to (to read, to write, to live). Although some may still advise the avoidance of split infinitives (usually by insertion of an adverb, such as in the phrase “to quickly understand”), this proscription—likely a holdover from Latin grammar, wherein the infinitive is a single word and cannot be split—has been relaxed. In some cases, moreover, clarity is better served by the split infinitive.


The authors planned to promote exercising vigorously. [Is it the exercising or the promotion of exercising that is vigorous?]


The authors planned to vigorously promote exercising. or The authors planned to promote vigorous exercise.


This examination was conducted to rapidly identify bleeding. [Changing the position of “rapidly” would alter the meaning of the sentence.]

7.4.6 Contractions.

A contraction consists of 2 words combined by omitting 1 or more letters (eg, can’t, aren’t). An apostrophe shows where the omission has occurred. Contractions are usually avoided in formal writing.