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

Spelling Out Numbers
Numbers and Percentages

Use words to express numbers that occur at the beginning of a sentence, title, subtitle, or heading; for common fractions; for accepted usage and numbers used as pronouns; for ordinals first through ninth; and when part of a published quote or title in which the number is spelled out. When spelling out numerals, hyphenate twenty-one through ninety-nine when these numbers occur alone or as part of a larger number. When numbers greater than 100 are spelled out, do not use commas or and (eg, one hundred thirty-two).

18.2.1 Beginning a Sentence, Title, Subtitle, or Heading.

Use words for any number that begins a sentence, title, subtitle, or heading. However, it may be better to reword the sentence so that it does not begin with a number.

Numerals may be used in sentences that begin with a specific year, but avoid beginning sentences with years if possible.

When a unit of measure follows a number that begins a sentence, it too must be written out, even if the same unit is abbreviated elsewhere in the same sentence. Because this construction can be cumbersome, rewording the sentence may be preferable (see 17.3, Format, Style, and Punctuation).

18.2.2 One Used as a Pronoun.

The word one should be spelled out when used as a pronoun or noun.

The investigators compared a new laboratory method with the standard one.

These differences may be concealed if one looks only at the total group.

William James uses the idea of the one and the many as the great challenge of the philosophical mind.

18.2.3 Accepted Usage.

Spell out numbers for generally accepted usage, such as idiomatic expressions. One frequently appears in running text without referring to a quantity per se and may appear awkward if expressed as a numeral. When one may be replaced by a or a single without changing the meaning, the word one rather than the numeral is usually appropriate. Other numbers, most often zero, two, and large rounded numbers, also may be written as words in circumstances in which use of the numeral would place an unintended emphasis on a precise quantity or would be confusing.

Any one of the 12 individuals might have been holding the winning ticket. [In this example, one may be superfluous. Depending on the intent, the following may be an equivalent sentence: Any of the 12 individuals might have been holding the winning ticket.]

The study was delayed by one problem after another.

Models were developed to allow for the inclusion of one-time variables.

The study participants frequently moved from one location to another.

On the one hand, the blood glucose concentrations were substantially improved; on the other hand, the patient felt worse.

Medical futility has become one of the dominant topics in medical ethics in recent years.

In one recent case, the malpractice award was $1 million.

We ought to bring together in one place all that we have learned on a given subject.

The outcome was a zero-sum gain.

Please include an example or two of the following scales.

I would like to ask the patient a question or two about her perception of her illness.

She hoped to be a neurosurgeon one day.

He quoted the Ten Commandments of Good Medical Practice, a guidebook for resident physicians (see 10.0, Capitalization).

Many of the mass-vaccination campaigns have been large, with tens of thousands of persons immunized, and expensive, costing as much as a half-million dollars.

During one of the laboratory runs, it was observed that samples from cases 1, 3, and 9 had faint electrophoretic bands attributable to suboptimal DNA quality.

But: During 1 of the 17 laboratory runs, it was observed. . . . (See 18.3.2, Consecutive Numerical Expressions.)

18.2.4 Ordinals.

Ordinal numbers generally express order or rank rather than a precise quantity. Because they usually address nontechnical aspects of the objects they modify, ordinals are often found in literary writing. The numerical expression of commonly used ordinals (1st, 2nd, 3rd, 4th, etc) may appear jarring and interrupt the flow of the text. For this reason, the ordinals first through ninth are spelled out.

The third patient was not available for reevaluation.

It finally has become second nature for the interns to establish an airway as the first part of any resuscitation effort.

The numeric form of ordinals greater than ninth is well established in literary texts (10th, 11th, and so on) except at the beginning of a sentence, title, subtitle, or heading. Use the following suffixes: -st, -nd, -rd, -th. The JAMA Network journals do not set these suffixes as superscripts.

Eleventh-hour negotiations resulted in the repeal of the Medicare Sustainable Growth Rate rule.

The pandemic will continue well into the 21st century.

He celebrated his 80th birthday while still in the hospital.

But: Some forms are spelled out by convention (eg, Twenty-fifth Amendment).

If a sentence contains 2 or more ordinals, at least 1 of which is greater than ninth, all should be expressed in numeric form.

Children in the 5th and 10th grades were included in the survey.

The first and third patients treated experienced complete remissions.