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Guide to Scientific Writing

MERLÍ. Manual d'estil i recursos lingüístics. Criteris lingüístics

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This guide offers you advice on scientific writing.

The purpose of scientific language and writing is to document, report and exchange knowledge in the most direct and objective way possible. Therefore, scientific texts must be:

  • Accurate and precise. Use simple and direct language and avoid vague or ambiguous words and sentences.
  • Clear and concise. Use simple and direct language and avoid unnecessary detail and superfluous words.
  • Objective. Support statements and ideas with appropriate evidence and avoid referring to personal thoughts or beliefs.



  • Text layout

    • Structure your text so that the content is easily identifiable: parts of the work, sections and subsections, lists, equations, graphs, diagrams, etc.
    • Apply the right font and size.
    • Use the same font throughout the text.
    • Make sure you align and justify the text.

  • Page numbers and title

    • Add page numbers when you start. The automatic indexing function of your word processor will incorporate these page numbers.
    • We recommend placing the page number at the foot of the page, to the right, and using just one digit, with no dot. Omit the page number on the first page.
    • Include the title of the work in the document header using the automatic function in your word processor. The title is usually left-justified.
    • Use the same font for your title as you have done for the text.

  • Chapters, sections and subsections

    • Number chapters, sections and subsections.
    • Apply the right font and size.
    • Remember that word processors allow you to mark sections and subsections automatically and to use them to create a table of contents or an index.

  • Lists

    • Use numbers, letters, bullets, etc. to list items.
    • To differentiate the items from the rest of the text, indent them slightly.

  • Tables, figures, graphs and equations

    • Place tables, figures, graphs and equations as close as possible to the paragraph in which you refer to them.
    • Centre-justify them.
    • Separate them from the text with a space.
    • Identify them with a number or letter.
    • Remember that word processors allow you to mark tables and figures automatically and to use them to create an index. You can also insert references to these tables and figures in the text.
    • When you are referring to a single figure, use an initial capital letter, e.g. In Figure 1, (…). If you are referring to more than one, use lower case, e.g. In figures 1 and 2, (…)



Paragraphs and sentences


  • Each paragraph must include a topic or subtopic.
  • Avoid single-sentence paragraphs and paragraphs that are longer than five sentences.
  • Structure paragraphs logically: introduction + development + conclusion.
  • Use the appropriate discourse markers to identify paragraphs.
  • Relate paragraphs to one another with the appropriate connectors.
  • Ensure cohesion between discourse markers and connectors.


  • Make sentences short and simple.
  • Keep parenthetical remarks to a minimum.
  • Put important ideas at the beginning.
  • Use the appropriate discourse markers to identify sentences.
  • Relate sentences to one another with the appropriate connectors.
  • Ensure cohesion between discourse markers and connectors.

Discourse markers and connectors

  • Use discourse markers and connectors to identify paragraphs and sentences (with regard to, in relation to, etc.).
  • Use discourse markers and connectors to relate paragraphs and sentences to one another.
  • As far as sequential markers are concerned, do not forget any of the elements and use them appropriately (first, second; firstly, secondly, etc.)
  • Avoid using on the one hand and on the other hand unless you really are contrasting items.



Vocabulary and terminology


  • Use formal and neutral language.
  • Use the words that are commonly used in a formal register.
  • Use verbs rather than nouns.
  • Use words with a specific meaning and avoid empty nouns and verbs.
  • Use adverbs sparingly.


  • To avoid confusion, ensure terminological consistency, that is, avoid using different terms to refer to the same thing: if you used wave action do not call it wave activity elsewhere in the text.
  • Consult the terminological resources that are available to find terms you were not aware of, to ensure that you are using a term correctly and to check terms in other languages.
  • Provide sufficient information on foreign terms and ensure that the reader knows what acronyms refer to.




Punctuation signs

  • Never put a comma between the subject and the verb.
  • Check the punctuation around parenthetical remarks: make sure there is a comma at the beginning and at the end.
  • Question marks and exclamation marks must be placed at the end of the sentence, with no space. There is no need for additional punctuation.
  • Ellipses: use just three dots, with no space before them, and do not over-use them. An etc. is preferred. Do not use an ellipsis and etc. in combination.
  • Brackets must be closed up to the phrase they are placed around; if they enclose a complete sentence, the punctuation sign must be placed before the closing bracket.
  • Use em dashes to set off parenthetical remarks, but do not over-use them. Em dashes (control + alt + minus sign) must be closed up to the rest of the sentence. If the parenthetical remark comes at the end of the sentence, omit the closing dash.
  • Remember that equations and formulae that are separated from the text but are part of a sentence must be punctuated just as other elements in the text are.



Symbols and acronyms

  • Symbols

    • Use physical, chemical and mathematical symbols in the manner established by international standardisation bodies as far as italics or roman type and capitalisation are concerned.
    • Do not put a dot at the end of a symbol.
    • Leave a space between the symbol and the quantity.
    • Use a non-breaking space (in Word, control + shift + space) between the symbol and the quantity so that they are not separated by a line break.
    • Symbols do not have plural forms.
    • With intervals or ranges, it is best to repeat the symbols for each value.
    • Write the symbols corresponding to names of persons with an initial capital letter.
    • Make sure you use superscript or subscript when necessary.

  • Acronyms

    • Write acronyms in capital letters.
    • Do not use dots in between the letters.
    • If you wish to use the plural, add an -s if the acronym does not stand for a plural already, e.g. ICT, ICTs.
    • Do not italicise acronyms that stand for words in other languages.
    • Use the acronym for the name in the language you are writing in, e.g. OECD, not OCDE.
    • The first time you use an acronym, use the full, written-out form, followed by the acronym in brackets. Use the acronym from then on.



Graphic features of the text

  • Font

    • Do not use more than one typographical resource to highlight an element of the text, e.g. italics + bold + underline.
    • Use italics for words in other languages, Latin terms, words or phrases in a metalinguistic sense, scientific names of animals and plants and titles of books.
    • Use bold for words you wish to draw attention to and for the titles of chapters, sections and subsections.
    • Do not over-use capitals; use them only when necessary.

  • Numbers

    • In any part of your work in which numerical data appear in isolation and surrounded by words, they must be written out if they contain three words or fewer, as long as they are not accompanied by a symbol.
    • Decimals: whole numbers and decimal numbers are separated by a dot (not a comma), with no spaces on either side.
    • Thousands: international standards endorse using a thin or non-breaking space to separate thousands from hundreds. A comma is also acceptable, but remember to be consistent throughout the text.



Equations and formulae

  • Follow the criteria set by international bodies for writing equations and formulae.
  • Use your word processor’s tools for writing equations and formulae.
  • Do not forget to apply the criteria to equations and formulae in the running text.

  • Equations

    • Consider whether an equation would be best presented in the running text or on a separate line.
    • If you set it off from the running text, leave a blank line before and afterwards.
    • Centre-align and indent equations that are part of the solution to a problem.

  • Mathematical formulae

    • Separate mathematical formulae from the text with blank lines before and afterwards, and centre-align them.
    • Leave a blank space between operators and digits.
    • Divide long formulae that are spread over more than one line at the points where any of the following signs appear: + – x =.
    • Do not divide operations in brackets, square brackets, etc.

  • Chemical formulae

    • Incorporate empirical and molecular formulae in the running text; separate semi-structural (condensed) and structural formulae from the running text with a blank line before and afterwards.
    • Do not divide chemical formulae.
    • Only divide chemical reactions using → or +.



Bibliography, in-text citations, references and footnotes

  • Footnotes

    • Footnotes are generally flagged by a superscript number that immediately follows the portion of the text that the note at the bottom of the page refers to.
    • The superscript number is placed after all punctuation marks except the dash.
    • Footnotes should appear on the same page as the portion of text to which they refer.
    • Use the same text size and font, although you can also use the same size as the text of the footnote (in this case, use a dot after the number).
    • Use a smaller size for the footnote than that of the body of the text. Remember that word processors allow you to create footnotes automatically.



How to produce a glossary of terms and write definitions

  • How to produce a glossary

    • Order the terms alphabetically.
    • Write the elements in a term in their natural order.
    • Introduce the full form of the term.
    • Do not include words that are not strictly part of the term.
    • Write the terms in lower case, except acronyms and proper nouns.
    • Verbs: use the infinitive.
    • Write the terms in the singular, except those that only have a plural form.
    • Include terms in other languages in the same list.

  • How to write definitions

    • Include only the specific sense in which you use the term in your text.
    • Express the principal sense in a single sentence. You can add complementary information later if you need to.
    • Use verbs in the present tense in the definition.
    • Start the definition with a capital letter and end it with a full stop.
    • Remember that a definition must not include the definition of another term.



Good writing practices

  • Enable the spell-checker when you start writing. Select the language you are writing in. Be especially careful not to mix British and American varieties of English. 
  • If there are fragments in other languages, select the right language.
  • Remember that spell-checkers have their limitations and may be a source of error.
  • If you copy a fragment from another text make sure there are no mistakes.
  • Eliminate double spaces with the find-and-replace function, as your spell-checker will not detect them.
  • Use the find-and-replace function with care; it can lead to unforeseen changes.
  • When you delete or replace parts of the text, make sure you do not leave behind truncated phrases, inconsistencies, and punctuation and other mistakes.
  • If you use machine translation, revise the result very carefully, as it may be lacking in quality.
  • As you develop the text, reread it, looking out for the different aspects considered in this guide (layers of revision). At the very least, reread it when you finish. It also helps to have someone else read your work and highlight parts of the text in which the writing may be unclear.



Oral presentation

  • Consult Class Talk for advice on improving your oral presentation in the classroom in English.