Types of Sources

When you find sources in your research, you will need to be able to distinguish which types of sources they will be categorized as when they appear in your research essay. These types are not always obvious or apparent, nor are they exclusive (a single source can be of several types simultaneously), but confusing them can cause problems with how you involve their ideas and information in your essay, and that can hurt your grade and harm your credibility as a writer. In other words, your professor will be able to see and distinguish the types of sources you are using in your research essay, so it is vital that you can too.

Types of Sources: Primary, Secondary, and Tertiary

Writers classify research resources in three categories: primary sources, secondary sources, and tertiary sources. These three types can come in any form: Websites, magazines, books, news stories, etc. What distinguishes them is not the publication category but instead how relevant they are to your subject and purpose.

Primary sources are direct, original sources of information or ideas. They are generally the best sources to use in research essays.

But whether a source is primary relies on your subject and purpose. For example, if you’re writing about free speech in the Constitution, then the First Amendment to the Constitution is your primary source. A Wikipedia entry about the First Amendment would not be a primary source. But this would change if your subject or purpose changed, so if you were writing an essay about how Wikipedia’s entry influences what people think free speech is, then Wikipedia is now your primary source.

The following types often end up being primary sources:

  • Research articles
  • Literary texts
  • Historical documents such as diaries or letters
  • Autobiographies or other personal accounts

Secondary sources are in-depth analyses of, interpretations of, and discussions about primary sources. They are often useful and insightful supplements to include in research essays, for they can help you and your audience contextualize and make clear sense of primary sources.

For example, if you’re writing about the First Amendment, you might read articles about legal cases that involved First Amendment rights, or editorials expressing commentary on the First Amendment. These sources would be considered secondary sources because they are one step removed from the primary source of information.

The following types often end up being secondary sources:

  • Magazine articles
  • Biographical books
  • Literary and scientific reviews
  • Television documentaries

Tertiary sources are less-engaged summaries or surveys of secondary or primary sources. These can be helpful guides when you are beginning your research, but they are rarely good sources to use in research essays.

For example, if you’re writing about the First Amendment, then you might read a Wikipedia page on it, or a textbook section explaining it. These would be tertiary sources. They are helpful for teaching you the basics of a subject, and for finding out what the primary and secondary sources are for it, but tertiary sources are generally weak as sources themselves.

The following types often end up being tertiary sources:

  • Encyclopedias
  • Course textbooks
  • News articles
  • Introductory or how-to Websites or videos

Keep in mind that your subject and purpose determine the kinds of primary and secondary sources you should seek and use in your essay. If you are writing a research essay about reality television shows, you will need to use some reality shows as a primary source, but secondary sources, such as a reviewer’s critique, are also important. If you are writing about the health effects of nicotine, you will probably want to read the published results of scientific studies, but secondary sources, such as magazine articles discussing the outcome of a recent study, may also be helpful.

Types of Publications: Scholarly, Trade, and Popular

In your research, you will encounter three very different types of publications: scholarly (including peer-reviewed), trade, and popular. Because all three types can cover the same subjects, they can sometimes seem similar to those new to research, but is important that you learn to distinguish among them. These types can appear on Websites, or within databases, or in print.

Scholarly publications (sometimes called academic publications) present reports and articles written by experts in academic or scientific fields. When you hear of scientists reporting new results or discoveries, or research teams finding new correlations or statistics, or scholars presenting important theories or analyses, that is because these are published in scholarly journals.

  • Audience: other experts, scholars, and academics; also student researchers
  • Content: long articles, lots of detailed information, many complex charts and graphs
  • Style: highly technical and academic, neutral and objective, information-heavy
  • Appearance: plain and serious
  • Citation: numerous citations, long bibliographies, many footnotes

Peer-reviewed publications are a special type of scholarly publication. They go through a long, difficult process of being evaluated by other experts and scholars in the field before they are even published. In other words, the expert authors must present their articles and reports to other experts—their peers—and get their approval first. That approval typically focuses on the legitimacy, reliability, and accuracy of the methods, sources, and theories used in the writing. Once this review by peers is complete, it can be published, and this peer-reviewed publication is therefore the most reliable type of publication that exists.

All peer-reviewed publications are scholarly, but not all scholarly publications are peer-reviewed. Both types are good sources to use in research essays, but peer-reviewed will generally be the best.

Because scholarly articles tend to be so long and detailed, they can be difficult to skim in order to find out whether they might be useful for your research. This is why they often contain abstracts.

Abstracts are short summaries of long scholarly articles or reports. These summaries are normally about one paragraph in length, and they explain what the article or report covers, what its methods or sources are, what its findings are, and what the authors’ conclusions are. Abstracts are found at the beginning of the article, and sometimes in the database information for the article. The whole purpose of abstracts is to make research easier on you by letting you know right away what the article or report contains.

Trade publications present articles, reports, and trends written by professionals in industries or business and technical fields, or by professional writers with experience and knowledge of the trade. When engineers learn about new technology to purchase and use, or physicians learn about drugs to prescribe, or business owners learn new methods to employ, they do so by reading trade publications.

  • Audience: other professionals within the industry or field; also experienced clients and consumers
  • Content: medium-length articles, news, illustrations and photos, advertisements related to the trade, industry, or field
  • Style: commercial, persuasive with some professional objectivity, specialized in its terminology and jargon
  • Appearance: vivid and state-of-the-art
  • Citation: some footnotes and bibliographies of sources

Trade publications can be useful for many types of research essays, but you will need to evaluate them closely since they can include biased information in attempts to sell or promote for profit.

Popular publications present articles, news, and opinions written by journalists and freelance writers. Most of the magazines, journals, and news sources you encounter on a daily basis, such as The New York Times, Time Magazine, USA Today, and The Wallstreet Journal, are popular publications.

  • Audience: general, everyday readers
  • Content: short- and medium-length articles, information tidbits, news, illustrations and photos, advertisements about common products and services
  • Style: entertaining, persuasive, commercial, accessible, sometimes provocative and controversial
  • Appearance: glossy and stylized
  • Citation: very few official citations, sometimes brief references within articles

Popular publications can be useful sources for examples in research essays, but they are not typically strong as sources for important information or ideas. They can often demonstrate what the common consensus or controversy on an issue is, and they can help point you toward better secondary and primary sources. But they will need to be evaluated very carefully, for they are almost always biased in selecting what kind of information to present, and how.

Terminology for Publication Forms

  • Book: a general term for a long work of any genre, often 50,000 words or more
  • Novel: a fiction book, which means the ideas and events it contains were imagined for entertainment or literary purposes
  • Story: a short work of fiction, often less than 10,000 words
  • News story: a short report for the general public of real, current events
  • Essay or article: a short work of non-fiction, often less than 10,000 words
  • Textbook: a non-fiction book used to teach you something, often including summaries, glossaries, comprehension questions, and other study aids
  • Journal, review, or magazine: a collection of articles and essays, or of stories, often one that recurs every so often as issues
  • Periodical: a collection of articles or essays that comes out on a regular basis, such as a newspaper or magazine
  • Reference book: a non-fiction book that presents information collected in lists or entries, such as a dictionary or encyclopedia
  • Op-Ed or opinion piece: an argumentative or opinionated article often published within news sites or journals, as opposed to purely informative reports or articles. These are not the same as unreliable sources that are secretly biased, fake, etc.; instead, these are openly clarified as debatable positions and arguments and are thus legitimate in that they are what they say they are.
  • Literature or literary works: writings that are intended to be artful, often fiction, but can be in the form of poems, plays, scripts, and songs
  • Biography: non-fiction about a person’s life
  • Autobiography: non-fiction about the author’s own life
  • Anthology: a collection of writings, often of literary works


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