How to write an annotated bibliography (with examples)

An annotated bibliography is a list of sources in which each citation is followed by a short paragraph, the annotation, that summarizes, evaluates or reflects on the source. Instructors assign them to check that you have read your sources closely, and researchers write them for themselves as the first step of a literature review. This guide covers what goes in an annotation, how long it should be, and how to format the whole thing.

What an annotated bibliography is for

A plain bibliography tells the reader what you used. An annotated bibliography also tells them what each source says, how good it is and why it matters to your project. Writing one forces you to engage with each source rather than skim it, and it leaves you with notes you can turn directly into a literature review.

The three kinds of annotation

Annotations do up to three jobs. Your assignment may ask for one, or for all three together:

• Descriptive, or summary: what the source is about, its main argument or finding, and how the author got there. It reports without judging.
• Evaluative, or critical: how strong the source is. Consider the methods, the sample, the evidence and the author's expertise, and compare it with other sources.
• Reflective: how the source fits your own research. Does it support your argument, challenge it, or supply a method you will use?

Most good annotations combine all three in a single paragraph: two or three sentences of summary, one or two of evaluation, and one of reflection.

How long should an annotation be?

Most annotations run between 100 and 200 words, about one solid paragraph. Some assignments ask for a few sentences; some research projects use longer notes. When your instructions give a length, follow them. When they do not, aim for around 150 words and spend them on what is most useful, not on restating the abstract.

How to write one, step by step

1. Choose your sources. Select the ones that bear directly on your question, with a mix of key studies, reviews and recent work.
2. Read each source with a purpose. Note the research question, the method, the main findings and the limitations as you go.
3. Write the citation in the required style, exactly as it would appear in a reference list.
4. Summarize the source in your own words. Lead with the main finding or argument, then the approach.
5. Evaluate it. Say what makes it strong or weak, and how it compares with the other sources on your list.
6. Reflect on its use. Say in one sentence what this source does for your project.

Formatting the bibliography

• Order the entries alphabetically by the first author's last name, as in a normal reference list.
• Format each citation in your required style, with a hanging indent.
• Put the annotation directly below its citation, indented as a block, usually in the same font and spacing as the rest of the document.
• Title the page the way your style or instructor asks, for example "Annotated Bibliography".

If you are not sure which citation style to use, APA vs MLA vs Chicago explains the differences.

Example in APA style

The source below is invented for illustration. The citation comes first, then the annotation.

Rivera, L., & Chen, D. (2021). Short sleep and next-day working memory in college students. Journal of Student Health, 14(2), 101-115.

Rivera and Chen tested whether a single night of short sleep impairs working memory the next day. In a within-subject experiment, 64 undergraduates completed an n-back task after a normal night and after a night limited to five hours; accuracy fell on the harder task conditions after short sleep, while reaction times did not change. The design controls for individual differences well, but the sample is small and drawn from one university, and the study measured only the following day, so it cannot speak to longer-term effects. The authors note this limitation themselves. This study gives my project its clearest experimental evidence for an acute effect, and its n-back procedure is a model for the task I plan to use.

The same entry in MLA style

Rivera, Luis, and David Chen. "Short Sleep and Next-Day Working Memory in College Students." Journal of Student Health, vol. 14, no. 2, 2021, pp. 101-15.

The annotation itself does not change between styles. Only the citation above it does.

Common mistakes to avoid

• Copying or lightly rewording the abstract. An annotation should show your reading, not the author's summary of their own work.
• Summary without evaluation, when the assignment asks for evaluation. "This study found X" is half an annotation.
• Vague evaluation, such as "this is a useful source". Say what makes it useful or limited.
• Inconsistent citation formatting between entries.
• Annotating sources you have not fully read. Readers can tell, and the annotation will not help you later.

From annotations to a literature review

An annotated bibliography is the raw material of a literature review. Once your sources are annotated, group them by theme, look for agreement and disagreement, and write paragraphs that make a point using several sources at once. How to write a literature review picks up exactly where this guide ends, and How to read a scientific paper can speed up the reading that comes first.

Keeping annotations in Mosaic

In Mosaic, each paper in a project keeps its own highlights and notes, so an annotation lives next to the source it describes. When you write, the Word and Google Docs add-ins insert the citation in the style you need.