Abbreviations, acronyms and numbers - simple things that most writers take for granted. That is, most writers do not feel that they need any special attention. However, in scientific writing, nothing should be taken for granted, and there are several considerations when including these things in your manuscript.

Abbreviations are shortened forms of a complete word, sometimes followed by a period but sometimes not. Some common abbreviations are:

  • Fig. (figure)
  • d (day)
  • h or hr (hour)
  • min (minute)
  • s or sec (second)
  • ml (milliliter)
  • Jan. (January)


  • Of course there are many other abbreviations, and their use is acceptable and often preferable. However, journals have varying rules for which abbreviations can be used without definition. It is vital that you check the journal's guidelines for accepted abbreviations. For example, some publications accept abbreviations for time (e.g. second, minute, hour, day) while others do not. Publications rarely accept abbreviations for months (e.g. Jan. for January) within the text of the manuscript; however, common abbreviations are accepted within figures and tables. (If they are not well-known, define them.) The word 'figure' often may be abbreviated as 'Fig.' However there are special rules for this usage. It is often abbreviated when it falls within parentheses, and it can only be abbreviated when followed by a number or numbers. When it is the first word of any sentence, 'Figure' must be spelled out, and picky journals will also require it to be spelled out at the beginning of the actual figure legend. Do not abbreviate units of measurement without a number; "Several ml. were added" is wrong. "Several milliliters were added" is correct.

    Because 'Fig' is the most commonly misused abbreviation in scientific writing, it warrants its own examples:
    Fig. 1 shows the data. (As the first word of the sentence, 'figure' must be spelled out)
    Figure 1 shows the data.
    The data are shown in the Fig. (only abbreviate when a number follows)
    The data are shown in Fig. 1.
    Acronyms: Acronyms, or initialisms, are formed by the first letters of a group of words, sometimes pronounced as a word (e.g., ANOVA for analysis of variance) and sometimes not (e.g. MRI for magnetic resonance imaging). Again, it is essential that the instructions the publication gives to authors be followed exactly. Those instructions should include a list of acronyms that are accepted without definition. If you are a medical researcher and are submitting to a journal outside of your particular field of study, do not assume that this journal will accept the same acronyms as those within your field. Reviewers, referees, and editors find it annoying when these instructions are not followed, increasing the chances that your manuscript will not be accepted. It may also give them the impression that the manuscript has already been rejected by another publication, because they assume you are following some other journal's instructions. If a particular acronym is not listed by the journal, it must be defined at first instance. Here are examples of the incorrect and correct ways to define an acronym in a scientific journal:
    CT (Computed Tomography)
    Computed Tomography (CT)
    In the abstract, it is best to avoid using unfamiliar acronyms because they will stil need to be defined at first instance there, and again at first instance in the body of the article. Simply spell out the term in full, unless it is used several times within the abstract.

    Two important guidelines for acronyms:

    1 - "When in doubt, spell it out."

    2 - Check the journal's "Author's Instructions" for:

  • Accepted abbreviations for units of measurement.
  • Accepted acronyms that do not need defining.
  • Use of acronyms in the article title and abstract.
  • Numbers: Some journals will specify how to treat numbers, however most do not. Below are some conservative rules (in scientific writing, conservative is best) to follow when deciding when to spell out numbers and when to use Arabic numerals(i.e. 1, 2, 3...). The following information was taken from "Successful Scientific Writing" by J. Matthews, et al.

    When to use Arabic numerals
    RULE EXAMPLES
    All numbers 10 and above Trial 13
    35 animals
    16 genera of legumes
    All numbers before a unit of measurement 10 cm long
    35 mg of the drug
    Numbers with decimals 7.38
    Numbers that represent statistical or mathematical functions or results, percentages or ratios. Multiply by 5.
    fewer than 6%
    3.75 times as many
    the 2nd quartile
    Numbers below 10 that are grouped for comparison with numbers 10 and above in the same sentence. 4 of 16 analyses
    3, 10, and 23 patients, respectively.
    lines 2 and 21
    Numbers that denote a specific place in a numbered series, parts of a book or manuscript, tables, figures, and each number in a list of four or more numbers Trial 6
    Group 2
    Table 4
    The groups consisted of 5, 9, 1, and 4 rats, respectively.
    When to write numbers as words
    RULE EXAMPLES
    All numbers below ten Five conditions
    the experiments were performed four times
    a one-tailed t-test
    a three-way interaction
    numbers below 10 that are grouped for comparison with numbers also below 10 the second of four stimuli
    five of eight living animals
    in six cases
    Any number that begins a sentence, title or heading - note hyphens with 2 or more words. Sixty-nine percent of the sample was contaminated.
    Thirty-six patients were enrolled in the study.
    Common fractions One quarter
    reduced by half
    a three-quarters majority
    The numbers zero and one are more easily read when spelled out. a one-line computer code
    zero-based budgeting
    Only one patient survived.
    As mentioned above, never start a sentence with a numeral. However, large numbers are awkward and the sentence can often be re-written.
    550 ml of hydrochloric acid should be added.
    (Correct but awkward)
    Five hundred fifty milliliters of hydrochloric acid should be added.
    The patient was 30 years old.
    A 30-year-old patient was admitted to the hospital.
    There are certain cases in which words and numerals need to be combined in order to make the text more readable - for example when they appear as back-to-back modifiers.

  • two 13-ml aliquots
  • three 96-well plates


  • Also, if more than two numbers appear back-to-back in a string, rewrite the phrase.
    six 3-5 day intervals
    six intervals of 3-5 days each
    - Tips Introduction
    - General Tips
    - The Proper Use of Verb Tense
    - Taking Apart Long Strings of Nouns and Adjectives
    - Commonly Misused Words (1)
    - Tables and Figures
    - Abbreviations, Acronyms, Numbers