Citing your sources means giving credit to the original author or creator whenever you use their ideas, words, or data in your own work. Every citation has two parts: a brief marker in the text itself (an in-text citation) and a full entry in a list at the end of your paper. The exact format depends on the citation style your class or publication requires, but the core principle is the same across all of them.
When You Need a Citation
You need to cite a source any time you quote someone’s exact words, paraphrase their ideas in your own language, or reference specific facts, statistics, or findings that came from someone else’s work. This applies whether the source is a book, a journal article, a website, a podcast, or a conversation with an AI chatbot.
The one broad exception is common knowledge: facts your audience would already be expected to know. “The Earth orbits the Sun” doesn’t need a citation. But “common knowledge” depends on context. A statistic that seems obvious in a medical journal might need a source in a general-interest essay. The Office of Research Integrity puts it simply: when in doubt, provide a citation.
Pick the Right Citation Style
Your instructor, journal, or publisher will usually tell you which style to use. If they don’t, the norm depends on your field:
- APA is the default in psychology, education, nursing, business, criminal justice, social work, and most social sciences.
- MLA is standard in English, creative writing, film, and other humanities courses focused on language and literature.
- Chicago comes in two flavors. The Notes-Bibliography version (footnotes plus a bibliography) is preferred in history, art history, music, and international relations. The Author-Date version works more like APA and is common in economics and anthropology.
If your assignment doesn’t specify, APA and MLA are the most widely taught and accepted in undergraduate work. Pick one and apply it consistently throughout your paper.
How In-Text Citations Work
An in-text citation is the short reference you place inside your paragraph to point the reader toward the full source. In APA style, you use the author’s last name and the year of publication, like (Jones, 1998). If you’re directly quoting, add a page number: (Jones, 1998, p. 199). For quotes spanning multiple pages, use “pp.” and an en dash: (Jones, 1998, pp. 199–201). When you’re paraphrasing rather than quoting, the page number is optional, though including one helps your reader locate the information in a long source.
MLA takes a different approach. Instead of the year, you include the author’s last name and the page number with no comma: (Jones 199). Chicago Notes-Bibliography uses footnotes or endnotes, placing a superscript number in the text that corresponds to a note at the bottom of the page or end of the document.
Regardless of style, every source you cite in the text must appear in your final reference list, and every entry in your reference list should correspond to a citation somewhere in the text.
Building Your Reference List
The reference list (called “Works Cited” in MLA or “Bibliography” in Chicago) sits at the end of your paper and gives readers enough information to find each source themselves. A typical entry for a book includes the author’s name, the year of publication, the title, the publisher, and sometimes a URL or DOI. A journal article adds the journal name, volume, issue number, and page range.
Formatting details matter here. In APA, only the first word of a book or article title is capitalized in the reference list, even though you capitalize major words when mentioning that title in the body of your paper. In MLA, titles of longer works are italicized and titles of shorter works go in quotation marks. These small differences are easy to miss, which is why checking a style guide or using a citation tool saves time.
Citing Websites, Social Media, and AI
Modern research pulls from far more than books and journals. For a website, you generally need the author (or organization), the page title, the site name, the publication or update date, and the URL. If no author is listed, the organization or site name takes that spot.
AI-generated content now has its own citation rules. In APA style, the author of an AI output is the company that built the tool, not the AI itself, because authorship requires a living person who can take responsibility for the work. A reference for a specific AI chat includes the company name, the date of the chat, the title you give the conversation, a bracketed description like “[Generative AI chat],” the tool or model name, and the URL of the chat if one is available. For example, citing a ChatGPT conversation would list OpenAI as the author and the date you used it. You should also keep a record of the prompts you used, and include them in an appendix or supplemental section if they would help your reader understand your process.
When citing an AI tool in general rather than a specific conversation, the date is the year the tool was most recently updated, and the title is the tool’s name in italics.
Quoting vs. Paraphrasing
A direct quote reproduces someone’s exact words and goes inside quotation marks. In APA, if a quote runs 40 words or longer, you format it as a block quote: start it on a new line, indent the entire passage half an inch from the left margin, and drop the quotation marks. The parenthetical citation goes after the closing punctuation of the block, not before it.
A paraphrase restates the original idea in your own words and sentence structure. It still needs a citation. Changing a few words while keeping the same structure isn’t paraphrasing; it’s too close to the original and can count as plagiarism. Genuine paraphrasing means you’ve absorbed the idea and expressed it freshly. When your source doesn’t have page numbers (a website, for instance), you can reference a paragraph number, section heading, chapter, or table number instead.
Tools That Format Citations for You
You don’t have to memorize every punctuation rule. Citation management software stores your sources, generates formatted citations, and inserts them directly into your document. The most popular options work slightly differently.
- Zotero is free for anyone, works with Microsoft Word, Google Docs, and OpenOffice, and stores unlimited citations on your local computer. A browser extension lets you save sources with one click while you research. It’s the easiest to learn and a strong default choice for most students.
- Mendeley is also free and is especially good for managing large collections of PDFs. It works with Word, OpenOffice, and LaTeX. You can share citation groups with up to 10 other users, which is helpful for collaborative projects. Free cloud storage is capped at 2 GB for personal files.
- EndNote is a paid tool (often available at an academic discount through universities) with deep integration into Word. It’s more common among graduate students and researchers managing very large libraries across multiple projects.
All three let you switch citation styles with a few clicks, so if a professor asks you to reformat from APA to Chicago, the software handles it automatically.
A Simple Process to Follow
Start collecting your sources from the moment you begin researching, not the night before your paper is due. Save each source to a citation manager or a running document that includes the author, title, date, and URL or publication details. As you write, insert an in-text citation every time you draw on someone else’s work. When your draft is finished, generate your reference list using your citation tool or format it manually by following the style guide your assignment requires.
Before submitting, do a quick cross-check. Read through your paper and confirm every in-text citation has a matching entry in your reference list. Then scan your reference list and make sure every entry actually appears somewhere in the text. This two-way check catches orphaned references and uncited sources, both of which can cost you points or credibility.