How to Cite Correctly: Rules, Types of Citation, Examples

In front of you sits a paragraph that makes your argument better than you could. Copy it word for word and you need quotation marks. Reword it, and most people assume the problem has gone away.

Citing correctly means making it clear, for every borrowed idea, where it came from, precisely enough that another reader can look up the passage. Word-for-word material sits inside quotation marks, reworded material sits in your own sentences, and both carry a citation with author, year and page. Federal law defines plagiarism for funded research, but for your coursework the binding rule is your school's honor code.

📌 The key points

• Plagiarism is using another person's work without appropriate credit.
• Rewording without a citation still counts as plagiarism.
• Federal law excludes self-plagiarism, most honor codes do not.
• APA, MLA and Chicago each name the source list differently.
• Your course syllabus outranks every general rule of thumb.

Why citing is required and how federal law defines plagiarism

Citing is not a formality. It is the condition that keeps your work checkable: anyone reading a claim must be able to look up what it rests on. Where the citation is missing, the borrowed thought looks like your own, and that confusion is what turns the borrowing into plagiarism.

The United States has a federal definition, and it is unusually precise. Under 42 CFR § 93.227, plagiarism means the appropriation of another person's ideas, processes, results or words without giving appropriate credit. That regulation governs research misconduct in work funded by the Public Health Service, not undergraduate coursework, but it is the clearest wording available anywhere in American law.

Why rewording alone does not replace a citation

The regulation names ideas, processes and results before it mentions words. That ordering settles the most common misconception about citing: putting a borrowed thought into your own sentences without crediting the source is the same act as copying it out. The text looks different, the idea underneath still belongs to someone else. Paraphrase is treated on equal terms with quotation throughout this guide for exactly that reason.

Where federal law and your honor code part company

One detail in the 2024 revision of the regulation surprises almost everyone who reads it. Section 93.227 states expressly that plagiarism does not include self-plagiarism, and that self-plagiarism and authorship disputes do not meet the federal definition of research misconduct. Reusing your own earlier text is therefore not a federal offense.

Your university almost certainly takes a different view. Honor codes and course policies routinely treat submitting the same paper in two courses as academic dishonesty, and they are entitled to, because the federal rule governs funded research rather than grading. The practical takeaway is simple: never argue a coursework case from federal law. What happens once a case is opened is covered in our guide to plagiarism checking for your thesis.

Direct quotation: copying word for word without changing anything

A direct quotation reproduces a passage from another source exactly, marked with quotation marks and followed by a citation including the page number. Spelling, punctuation and emphasis stay as they appear in the original, even where they are outdated or wrong.

That duty of accuracy is why direct quotation is used far more sparingly than most students expect. Copying a passage shows only that you found it, not that you understood it. Quotation earns its place with definitions, with unusually well-turned formulations, and wherever you go on to analyze the exact wording.

You may intervene inside a quotation, but every intervention has to be visible. Four conventions cover almost everything that comes up in a term paper or thesis.

• Omission: an ellipsis inside square brackets, written as [...]. Older guides also distinguish between one and several omitted words, which is no longer usual.
• Your own addition: place it in square brackets and label it, for example [my addition].
• Error in the original: put [sic] straight after it so readers can see the mistake is not yours.
• Your own emphasis: record it in the citation, usually with the note "emphasis added".

When a quotation becomes an indented block

Longer quotations are set as an indented block and lose their quotation marks in the process. The threshold is set by the citation style, and the three American styles do not agree. Under the APA guidelines on quotations, anything from 40 words upward is a block quotation, indented half an inch and without quotation marks.

MLA 9 uses lines instead of words and blocks a prose quotation from more than four lines, or a verse quotation from more than three. Chicago recommends blocking from roughly five lines and treats the figure as guidance rather than a rule. Where your syllabus names a different threshold, follow the syllabus.

💡 Tip

Note the page number at the moment you copy a passage, not later. Quotations without page numbers are the single most common reason for paging back through entire books in the last days before a deadline.

Paraphrase: your own words, and still a citation

A paraphrase restates the content of another source in your own words and still carries a full citation. The quotation marks fall away, the credit does not. Paraphrase is the normal case in academic writing and direct quotation the exception, not the other way round.

A genuine paraphrase changes sentence structure and vocabulary, not just individual words. Swapping in synonyms while leaving the original syntax intact produces a badly disguised quotation rather than a paraphrase. Similarity software finds those passages reliably, and instructors notice them through the break in writing style.

Do you need a page number in a paraphrase?

The three major American styles answer that differently, and the difference causes real confusion. APA 7 recommends a page or paragraph number for a paraphrase but does not require one, suggesting it mainly for long works. MLA expects the page number, because the in-text citation is built around it. Chicago notes carry it as a matter of course.

Correct as of September 2026, subject to change.

Signal phrases do the work that quotation marks cannot

Because a paraphrase carries no quotation marks, the reader needs another cue that a position belongs to someone else. Signal phrases supply it: "Carter argues", "Carter found", "Carter suggests". The verb you choose also tells the reader how much weight the source carries, which is why "claims" and "demonstrates" are not interchangeable.

The practical benefit shows up over longer passages. If a paragraph opens with a signal phrase and closes with the citation, everything between the two is visibly attributed. Without that frame, a citation at the end of a paragraph leaves the earlier sentences looking like your own analysis, which is the error described further down this page.

Indirect source: when you cannot reach the original

An indirect source is a statement you have not read in the original but found quoted in another work. American style guides mark it with the phrase "as cited in" or "qtd. in", giving both works in a single citation. You name two sources and have read only one of them.

Citing an indirect source is acceptable only where the original really is out of reach, for instance an out-of-print volume, an unpublished manuscript or a source in a language you do not read. Out of reach does not mean absent from your campus library. Interlibrary loan costs you a few days and is the normal route.

The pattern looks like this in the two styles most common at American universities. The elements stay the same and only the order changes.

• APA 7, in the text: (Whitfield, 1998, as cited in Carter, 2023)
• MLA 9, in the text: (qtd. in Carter 45)

The source list carries only the work you actually held, so Carter in both cases. Listing both titles claims a reading that never happened, and an instructor who checks the original will notice.

⚠️ Careful

An indirect source inherits the errors of the intermediate work. Wrong dates, shortened claims and sentences lifted out of context pass unchecked into your paper. Where indirect sources cluster in one chapter, it reads to an instructor as a sign that the foundational literature has not been read.

Which sources you are allowed to cite

Before the question of how to cite comes the question of what may be cited at all. Two separate criteria decide it, and they are regularly confused: whether a source is traceable, and whether it is academically credible. A source has to satisfy both.

A source is traceable if it has been published and remains findable by a third party. That is purely a question of access. It is credible if its content meets academic standards, so it was produced transparently, reviewed by peers or an editor, and can be attributed to a responsible person or institution. That is a question of quality.

Sources that satisfy both criteria

• Journal articles from peer-reviewed publications, findable by DOI.
• Monographs and edited collections from university presses.
• Federal statistics, for example from the Census Bureau.
• Dissertations published through ProQuest or an institutional repository.

Sources that fail, and where exactly they fail

• Lecture slides are rarely publicly accessible and therefore usually not traceable.
• Wikipedia entries are traceable but name no responsible author, so they are not credible.
• Answers from language models cannot be reproduced and fail the traceability test outright.
• Tabloid coverage is traceable but not credible as evidence for factual claims.

The tabloid case shows why credibility cannot be settled in the abstract. Writing about Social Security policy, you would not take figures from that source. Writing about the media framing of Social Security policy, those articles are exactly what you cite, as material rather than as evidence. What decides is the role the source plays in your argument.

Online sources add a question of stability, because pages disappear and addresses change. Which details make a web source complete, and how to protect it against link rot, is covered in our guide to citing internet sources. For printed works, the same logic appears in our guide to citing books.

Choosing a citation style: four systems compared

A citation style decides where the citation sits and in what order its parts appear. Every style asks for the same substance, namely author, year, title and location. They differ in form rather than content, which is why the choice matters less than it feels like it does.

American styles split into two groups. Author-date and author-page systems put a short citation in parentheses in the running text. Note systems put it at the foot of the page and keep parentheses out of the text. Mixing the two in one paper is the most frequent formal error of all.

There is no nationally mandated citation style in the United States, and no federal agency prescribes one for coursework. Your syllabus comes first, even where it departs from what is usual in the discipline; where the syllabus says nothing, follow the style of the journals you are already reading in that field.

One difference between the styles is easy to overlook and costs points every semester. The list at the end of your paper carries a different name in each system: References in APA, Works Cited in MLA, Bibliography in Chicago. Submitting an APA paper headed Works Cited signals immediately that the style was applied from memory. The two systems used most widely outside the United States are covered in our guides to Harvard referencing and to footnote referencing.

Page numbers and sources that do not have them

The page number carries the citation the last step, from the work to the passage, and it is where appropriate credit becomes practical rather than theoretical. APA and Chicago abbreviate it as p. for one page and pp. for a range. MLA drops the abbreviation entirely and gives the bare number.

American styles do not use the abbreviations f. and ff. that appear in German and Austrian sources for a page and the following one. Every American style asks for the full span with a first and last page. A citation copied out of a European handout will therefore look wrong to an American instructor, and the reverse is equally true.

Sources without page numbers need a different locator, and this is where most online citations go wrong. APA 7 accepts a paragraph number, a section heading, or a heading plus paragraph number for a long section. MLA 9 asks you to leave the locator out entirely rather than invent one, which is the opposite instruction.

Timestamps follow the same logic for audio and video. A claim taken from a lecture recording is cited with the minute and second at which it occurs, so that a reader can jump straight to it. Omitting the timestamp turns a precise source into a two-hour search.

Common citation mistakes

Most penalties arise not from ignorance of citation rules but from the last days before a deadline, when citations are added afterward instead of recorded during reading. Four mistakes recur often enough to be worth a dedicated pass through the finished draft.

Each of the four takes minutes to check if you look for it deliberately. One sweep of the whole document is more efficient than working chapter by chapter. Where citing sits in the wider process is covered in our guide to academic working practice.

One citation at the end of a paragraph is meant to cover everything

A citation covers the sentence it sits in, not everything that came before it retroactively. Summarizing five sentences from a source and placing a single citation after the fifth leaves four sentences unattributed. The clean solution is a signal phrase at the start of the passage, such as "Carter distinguishes three approaches", with the citation at the end.

Two citation styles in one paper

Running a note system alongside an author-date system is the most common formal error in theses. It usually arises from reusing your own earlier papers written for different courses. Settle on one system early and check the chapter you wrote first, since that is where the older habit survives.

A quotation was quietly tidied up

A quotation in which a verb ending has been adjusted, a word inserted or old spelling modernized is no longer a quotation. Every alteration belongs in square brackets. Where the brackets make the sentence unreadable, that is a signal that a paraphrase would serve better at this point.

A source appears in the text but not in the source list

Every source cited in the text also appears in the References, Works Cited or Bibliography, and nothing appears there that the text never mentions. Both are obvious to an instructor skimming the back matter. The quickest way to find such gaps is to work through the list from the bottom up, searching for each entry in the text.

Conclusion

Citing well is less a matter of rule knowledge than of discipline while reading. Establish which style your syllabus requires, record author, year and page at the moment you read rather than afterward, and hold paraphrase to the same standard as quotation. Most problems are then solved before they arise.

Record it while you read and you will never have to search while you write. Almost every citation error is made afterward.

Where to go next

• Working with author-date citations? Harvard referencing: rules and examples
• Working with footnotes? Footnote referencing explained
• Want the whole research process? Empirical research: definition and guide

Collecting your own data instead of citing someone else's?

Results from your own survey are not cited at all, they are your data and belong in the methods section. With empirio.ai, an online survey tool from Germany, you can build one free of charge. How to structure the questions is set out in our guide to creating a questionnaire.