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Citing Sources

A guide to introduce how to cite your sources, avoid plagiarism, and use the right style guides to format your citations.

Citation Basics

Why cite?

As a university student, a large amount of your time is spent on research: you read academic books and journals; you write research papers, attend lectures and participate in classroom discussions. By doing all of this, you are not only consuming information, but are actively participating in the production and sharing of knowledge. The cycle of consuming, producing, and sharing knowledge in academia is called the scholarly conversation.

Consider, when you are researching, that you are having a conversation with the sources that you find—you respect other peoples' ideas and you are adding your thoughts new to the conversation. To learn more about the scholarly conversation and its role in academia, watch "Scholarship as Conversation" by McMaster Libraries below.


In addition to adding your voice to the ongoing scholarly conversation, you want to include sources in your research to:

Establish Intellectual Context

The best research comes from previous discoveries. Incorporating other people’s ideas into your writing allows you to stand on their shoulders as you explore your topic. When you cite sources, you become more credible by showing that you've been responsible in arriving at your position.

Give Credit Where Credit is Due

Most of us are familiar with this reason for citing sources: just as you want credit for your ideas, other scholars deserve credit for their work. By acknowledging the valuable work of other scholars, you establish a cooperative ethical framework of the exchange and discourse of ideas.

Lead Readers to Future Research

Scholarship is ongoing and collaborative. Rather than try to create ideas from scratch, we build on and extend ideas to create our own work. One scholar's sources can be an invaluable contribution to another scholar's research. In this way, acknowledging and citing your sources shows your audience where they might look to test, explore, and build upon your scholarship.

What is a citation?

A citation is the way you tell your readers that certain material in your work came from another source. It also gives your readers the information necessary to find that source again, such as:

  • the name of the author(s)
  • the title of the work
  • the name of the organization or publication that published the work
  • the date it was published
  • the volume, issue and/or page numbers of the work
  • whether the work is a print or electronic source
  • the name of the database where the source was found

Academic disciplines have varying expectations for how to list citation information. You should check with your instructor about the style they want you to use. When in doubt, remember that the goal of your citations is to help your audience consult your sources directly. Give enough information to make such retrieval easy.

To learn more about citations in college research, watch "What is Citing," below.

When do I cite?

When you cite a source, you show how your voice is part of an existing intellectual conversation. Working with sources can inspire your own ideas and enrich them, and your citing sources is the visible trace of that debt. However, it can be hard sometimes to identify when and how you should cite your sources.

Whenever you borrow words or ideas, you need to acknowledge the source. Some established guidelines about when sources should be acknowledged are:

When you quote your source directly

Most scholars realize that they must acknowledge a source when quoting a memorable phrase or sentence. Additionally, though, when a single word or two are used in a distinctive way, the source is usually establishing a new concept, and you must give acknowledge the source.

When you introduce facts found in a source

Facts that are generally accessible (the date of the Declaration of Independence, for instance) need not be cited to a particular source, but once you go up one level of detail, you probably need to cite the source (the number of people who signed the Declaration, for instance).

When you paraphrase or summarize ideas, interpretations, or conclusions you find in a source

Paraphrasing is your own version of essential information and ideas expressed by someone else, presented in a new form. It is a way you can include sources in your research without directly quoting source material. Anytime you do paraphrase information from a source, you need to specify where you got that information.

In other words ... if it did not come out of your own head, cite the source!

What gets cited?

You should cite any and every type of information source that you incorporate in your research. This can include:

  • Journal, newspaper, or magazine articles
  • Books and ebooks
  • Social media posts
  • Data or statistics
  • Art or media
  • Interviews
  • Maps
  • Websites

Just remember ... If you use it, you must cite it!

What is a citation style?

Academic disciplines have varying expectations for how to list citation information. All the styles require the same basic information ... it is the order of that information that varies. In part, this is because different academic fields emphasize different elements of a source when referring to previous research.

Which style should I use?

You should check with your instructor about the style they want you to use. If your instructor does not require a style, choose a citation style that is common in your discipline. Popular citation styles are:

  • APA (Social Sciences and Sciences)
  • MLA (Humanities)
  • Chicago
    • Notes - Bibliography (Humanities)
    • Author - Date (Social Sciences)

There are also styles from professional associations for specific disciplines, such as the American Sociological Association (ASA) or the American Chemical Society (ACS).

Here is a quick list of the core citation style guides are used in different disciplines:

  • AAA -- Anthropology
  • ACS -- Chemistry
  • AMA -- Medicine and Public Health
  • AP  -- Journalism
  • APA  -- Social Sciences
  • ASA -- Sociology
  • Bluebook -- Legal Documents
  • Chicago / Turabian  -- History, Art History  & some Social Sciences
  • CSE -- Sciences
  • IEEE -- Engineering
  • MLA -- English & some Humanities

The following guides provide in-depth information about the different citation styles:


To provide an overview of the difference between the three most commonly used citation styles, this chart from Purdue provides a side-by-side comparison of ALA 6th edition, MLA 7th edition, and the Chicago Manual of Style 16th edition.

  • to steal and pass off (the ideas or words of another) as one's own
  • to use (another's production) without crediting the source
  • to commit literary theft
  • to present as new and original an idea or product derived from an existing source

Plagiarism involves both stealing someone else's work and lying about it afterward … in other words, it is an act of fraud.


10 Types of Plagiarism


How to Avoid Plagiarism


Recommended Guides & Resources