How to Write an Abstract: A Five-Sentence Method, With Before/After Examples

November 9, 2026 · Research & citation

The abstract is the shortest part of a dissertation, lab report or research paper, and it is often the only part anyone reads. Examiners read it first; database users read it to decide whether to download the paper at all. Yet students usually write it in the last half hour before the deadline, by copying the first sentence of each section. This guide explains what an abstract has to do, gives a five-sentence method for building one from your finished paper, and shows a weak abstract rewritten into a strong one.

What an abstract is for

An abstract is a self-contained summary of a longer piece of work. "Self-contained" is the key word: someone who reads only the abstract should come away knowing what question you asked, how you tried to answer it, what you found and why it matters. It is not an introduction, which sets up the question and leaves the answer for later, and it is not a teaser that hides the result to keep the reader curious.

The UNC Writing Center distinguishes two main types:

• Descriptive abstracts say what kind of information the work contains, without giving results or conclusions. They are short, usually 100 words or less, and are common in the humanities and in conference programmes.
• Informative abstracts act as a surrogate for the work itself: they give the purpose, method, main results and conclusions. This is the type most coursework, dissertations and journal articles in the sciences and social sciences expect. UNC notes that an informative abstract is rarely more than 10% of the length of the whole work.

If your brief does not say which type you need, the word limit is a clue. A limit of around 100 to 120 words points to a descriptive abstract; 250 words or more points to an informative one. When in doubt, ask your tutor.

Check the brief before you write a word

Abstract rules differ more between courses and journals than almost any other part of a paper. Look for four things in your instructions or the style guide you have been given:

1. Word limit. Treat it as a hard ceiling. Under APA 7, abstracts are typically limited to 250 words, but many departments set their own limit for dissertations, and journals vary widely.
2. Structured or unstructured. Some fields, medicine and health sciences in particular, ask for a structured abstract with labelled headings such as Background, Methods, Results and Conclusions. Most coursework uses a single unbroken paragraph.
3. Keywords. Whether they are required, how many, and where they go.
4. Whether you need one at all. In APA 7, student papers do not include an abstract unless the instructor asks for one. Do not add one to a short essay "to look professional"; it eats into your word count and may not be marked.

Write it last

You cannot summarise a paper that does not exist yet. A draft abstract written at the start of a project is useful as a planning tool, but it describes the study you intended to do, not the one you did. Results change, a planned analysis gets dropped, the argument shifts. Write the final abstract after the paper is complete, then compare it line by line with the paper.

The UNC handout suggests a technique called reverse outlining: go through your finished paper and write one sentence that states the main idea of each section, then combine and condense those sentences. It forces you to find what each section actually says.

The five-sentence method

For a typical informative abstract of 150 to 250 words, aim for one or two sentences on each of five moves. The proportions matter: most weak abstracts spend half their words on background and leave the result as an afterthought.

These shares are a rule of thumb, not a requirement. For a humanities essay or a literature-based dissertation, "method" becomes the corpus or sources you examine and the approach you take, and "findings" becomes your argument and its main steps. If you wrote a literature review rather than an empirical study, the findings are the patterns, agreements and gaps you identified across the literature.

Before and after: a worked example

The example below is for a fictional undergraduate project. Here is a first draft, 91 words, written by copying opening sentences from each section:

Every sentence is grammatical, and almost none of them tells the reader anything. The context is generic, the aim is vague, the method has no detail, the result is withheld ("interesting", "some differences") and the conclusion could close any paper on any topic. Here is the same abstract rewritten with the five moves, 135 words (all figures are invented for the illustration):

Notice the changes. The opening sentence states a specific gap rather than a truism. The aim names the population and both questions. The method gives the design, the sample and how outcomes were measured. The findings give actual results. The final sentence states a limitation honestly and draws one concrete implication. Every figure in a real abstract must, of course, appear in the results section of the paper.

Keywords

Keywords help databases index your work and help readers find it. The APA Style guidelines on abstracts and keywords place them on the line below the abstract, introduced by the label Keywords: in italics, with the keywords themselves in lowercase (except proper nouns), separated by commas, and with no full stop at the end. APA suggests three to five keywords. Choose terms a researcher would actually type into a search box, including synonyms that are not already in your title. Our guide to finding scholarly sources shows how database searches use those terms from the other side.

Common mistakes

• Withholding the result. "The results are discussed" is the most common weakness. State them.
• Adding new information. The abstract must not contain claims, data or sources that do not appear in the paper.
• Citations and definitions. Avoid references to other works and definitions of terms unless your field's conventions require them; the abstract summarises your work, not the literature.
• Undefined abbreviations. Spell out an abbreviation the first time it appears in the abstract, even if the paper defines it later.
• Exceeding the limit. Some submission systems cut the text off at the limit, so the final sentence, usually your implication, disappears.

Final checklist

1. Could a reader who sees only the abstract state your question, method, main result and conclusion?
2. Does every figure and claim match the paper exactly?
3. Is it within the word limit and in the required format (single paragraph or structured)?
4. Are the tenses consistent? Past tense for what you did and found, present tense for what the results suggest.
5. Are the keywords there, in the right format, if your brief requires them?

One last distinction: when you build an annotated bibliography, remember the difference: an abstract is the authors' own summary of their work, and your annotation should go beyond it.

Sources

• The Writing Center, University of North Carolina at Chapel Hill, Abstracts.
• American Psychological Association, Abstract and keywords guidelines (APA Style, 7th edition).

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