APA vs MLA vs Chicago vs Harvard vs IEEE: which citation style should you use?

The short answer is: use whichever style your instructor, department or journal tells you to. If they haven't said, ask. The rest of this guide helps you recognise the five most common styles and understand how they differ.

What a citation does

Every citation system has two parts that point at each other. The in-text citation (or footnote) tells the reader, at the exact spot, that an idea or quote came from somewhere else. The reference list (or bibliography) at the end gives the full details so they can find the source. Styles differ in how those two parts look; they agree on what they're for: giving credit and letting readers check your work.

The five styles at a glance

• APA (American Psychological Association) is common in psychology, education, nursing and the social sciences. In-text citations use the author and year: (Sharma, 2022).
• MLA (Modern Language Association) is common in literature, languages and other humanities. In-text citations use the author and page: (Sharma 45). Your list is called “Works Cited”.
• Chicago is common in history and some humanities and in publishing. It has two systems: notes and bibliography (footnotes or endnotes) and author–date. Check which one your course wants.
• Harvard is an author–date style used widely in the UK, Australia and in business and economics. There is no single official Harvard guide, so universities publish their own versions. Follow yours.
• IEEE is common in engineering, computer science and IT. Citations are numbers in square brackets, [1], and the reference list is in the order you cite them.

The same book, five ways

Here is an imaginary book, Introduction to Learning Science by Priya Sharma, published by Orion Press in 2022, cited in each style. The details of punctuation differ between editions and institutions, so treat these as illustrations and check your own guide.

• APA 7: Sharma, P. (2022). Introduction to learning science. Orion Press. — In text: (Sharma, 2022)
• MLA 9: Sharma, Priya. Introduction to Learning Science. Orion Press, 2022. — In text: (Sharma 45)
• Chicago (notes and bibliography): Sharma, Priya. Introduction to Learning Science. New Delhi: Orion Press, 2022. — In a footnote: 1. Priya Sharma, Introduction to Learning Science (New Delhi: Orion Press, 2022), 45.
• Harvard (a common form): Sharma, P. (2022) Introduction to learning science. New Delhi: Orion Press. — In text: (Sharma, 2022)
• IEEE: [1] P. Sharma, Introduction to Learning Science. New Delhi, India: Orion Press, 2022. — In text: [1]

How to choose when nobody tells you

• Look at the assignment brief or the department's writing guide first.
• Look at recent papers in your field; they show the habit.
• If it's truly open, pick one and use it consistently. Consistency matters more than which style it is.

What needs a citation

Cite whenever you use someone else's words, ideas, data or images:

• Direct quotes. Put them in quotation marks (or a block quote for a long one) and cite them.
• Paraphrases. Rewording an idea doesn't make it yours; it still needs a citation. Changing a few words isn't paraphrasing.
• Facts and figures that aren't common knowledge, such as statistics, dates of specific events and research findings.
• Images, charts and tables that you didn't make yourself.

Common knowledge, like the fact that water boils at 100 °C at sea level, doesn't need a citation. If you're not sure whether something counts, cite it; over-citing costs you nothing.

How to paraphrase properly

1. Read the passage until you understand it, then close the source.
2. Write the idea from memory, in your own words and sentence structure.
3. Compare with the original to check you've kept the meaning and haven't copied its phrasing.
4. Add the citation.

Mistakes that cost marks

• Mixing styles in one document.
• Citing in the text but leaving the source out of the reference list (or the reverse).
• Missing details: author, year, title, publisher, URL or DOI.
• Citing something you haven't actually opened. If you cite it, read at least the relevant part.
• Citing a web page you can't find again. Save the URL, the title and the date you read it.
• Trusting an AI-generated reference. AI tools can produce citations that look right but refer to papers that don't exist. Open every source before you cite it.

Doing it faster, safely

Reference managers are worth learning if you'll write a lot. For a single assignment, Learnsable's citation generator takes URLs, DOIs or rough references, looks them up on the web, and builds the in-text citations and bibliography in your chosen style. It tells you which fields it couldn't find instead of making them up. You still verify each entry against the source and your style guide.

Quick answers

• Can I cite Wikipedia? Use it to find sources, then cite the original sources it points to. Many instructors don't accept it as a reference.
• Do I cite lecture slides or class notes? If you use their content, yes, and your style guide shows how. Ask your instructor if you're unsure.
• What if I can't find the author? Styles have a rule for this, usually starting the entry with the title or the organisation. Look it up in your guide.
• Which edition should I follow? The one your instructor names. Guides are revised from time to time, and details change between editions.