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What Is APA Style?
APA stands for American Psychological Association. It’s the citation and formatting standard created by psychologists and researchers who wanted a consistent way to present research across the social sciences.
APA (7th edition) = parenthetical author-year citations, sentence case titles, used in social sciences, education, and nursing.
Chicago (18th edition) = footnote/endnote system (Notes-Bibliography) or author-year format (Author-Date), title case, used in history, humanities, and theology.
The core difference: APA puts the citation in parentheses right after the quote. Chicago’s Notes-Bibliography style puts a superscript number in the text that links to a footnote or endnote, which then appears at the bottom of the page or at the end of the paper.
Both styles are respected and widely used. Which one you need depends on your discipline — not on which is “better.”
Today, APA 7th edition is the go-to format for papers in:
- Psychology
- Education
- Nursing and healthcare
- Sociology
- Political science
- Business research
APA is designed to help readers quickly identify when and who wrote a source. The parenthetical (author, year) format puts the citation right inside your sentence, so readers never lose track of where an idea came from.
What we recommend: If your professor or journal requires APA, stick with it. Don’t switch halfway through — consistency matters more than perfection. Use a citation manager (Zotero, Mendeley, or EndNote) to handle the formatting automatically. Our citation management tools comparison breaks down which tool works best for different needs.
What Is Chicago Style?
Chicago style is named after the University of Chicago Press and is maintained by The Chicago Manual of Style, which is updated every few years. It’s the oldest and most widely used citation system in the United States.
Unlike APA, Chicago has two separate citation systems, and knowing which one your assignment requires makes a big difference:
- Notes-Bibliography (NB) — Uses footnotes or endnotes with a superscript number in the text, followed by a full bibliography at the end. This is the default system for most humanities and history papers.
- Author-Date (AD) — Resembles APA more closely, using parenthetical citations with the author’s last name and publication year, but with different punctuation and capitalization rules.
Chicago 18th edition (released September 2024) is the current version. It streamlined several citation formats and removed chapter page ranges from bibliography entries — changes that most student guides haven’t caught up to yet.
Fun fact: The Chicago Notes-Bibliography system is unique because it allows scholarly commentary inside the note itself, not just a citation. That’s a feature APA does not support.
APA vs Chicago: Side-by-Side Comparison Chart
This is the comparison most students actually need — a detailed, row-by-row breakdown of how APA 7th edition and Chicago 18th edition handle the same source type. Every row includes a concrete example so you can see the formatting differences side by side.
Source Type 1: Book (Single Author)
| Formatting Dimension | APA 7th Edition | Chicago 18th Edition (Notes-Bibliography) | Chicago 18th Edition (Author-Date) |
|---|---|---|---|
| Title page | Title, author name, institution, course, instructor, date. Centered on one page. | Simple page with only the title, author name, and date. No heading hierarchy. | Same as NB — simple title page with title, author, date. |
| Heading levels | 5-level system (Level 1–5) with specific formatting for each (bold, italic, centered, indented). | Only 3 heading levels (Heading 1, Heading 2, Heading 3). Much simpler structure. | Same 3-level system as NB. |
| In-text citation | (Smith, 2024) | Superscript number in text → footnote or endnote entry | (Smith 2024) |
| Citation punctuation | Comma after author, comma before year | Footnote uses commas throughout; bibliography omits commas between elements | Comma after author, no comma before year |
| Author name format | Last name, Initials. (Smith, J. A.) | First name spelled out, last name first in bibliography. (Smith, John A.) | First name spelled out, last name first. (Smith, John A.) |
| Title capitalization | Sentence case: Only first letter of title and subtitle capitalized. The psychology of learning. | Title case: Major words capitalized. The Psychology of Learning | Title case: Major words capitalized. The Psychology of Learning |
| Place of publication | Not required in APA 7th. | No place of publication required (2024 update) | Same — no place of publication. |
| DOI formatting | Full URL: https://doi.org/10.xxxx/xxxx (no “doi:” prefix) |
Full URL: https://doi.org/10.xxxx/xxxx |
Full URL: https://doi.org/10.xxxx/xxxx |
| Year placement | Year in parentheses right after author: (Smith, 2024) | Year appears at the end of the bibliographic entry | Year right after author, no parentheses: (Smith 2024) |
| Bibliography / Reference list | Titled “References.” Alphabetical order. Hanging indent. | Titled “Bibliography.” Alphabetical order. Hanging indent. | Titled “References.” Alphabetical order. Hanging indent. |
Actual formatted example:
Click to expand — see exactly how the same book looks in each style
APA 7th Edition Reference:
Smith, J. A. (2024). The psychology of learning: How students retain information. Academic Press.
Chicago 18th Edition Notes-Bibliography (footnote):
1. John A. Smith, The Psychology of Learning: How Students Retain Information (Chicago: Academic Press, 2024), 45.
Chicago 18th Edition Notes-Bibliography (bibliography entry):
Smith, John A. The Psychology of Learning: How Students Retain Information. Chicago: Academic Press, 2024.
Chicago 18th Edition Author-Date:
Smith, John A. 2024. The Psychology of Learning: How Students Retain Information. Chicago: Academic Press.
Source Type 2: Journal Article
| Formatting Dimension | APA 7th Edition | Chicago 18th Edition (Notes-Bibliography) | Chicago 18th Edition (Author-Date) |
|---|---|---|---|
| In-text citation | (Jones & Lee, 2024) | Superscript number → footnote or endnote | (Jones and Lee 2024) |
| Author format | Last name, Initials. (Jones, R., & Lee, A.) | Full first names. (Jones, Robert, and Ashley Lee) | Full first names. (Jones, Robert, and Ashley Lee) |
| Article title | Sentence case. “How spaced repetition improves memory.” | Title case. “How Spaced Repetition Improves Memory.” | Title case. “How Spaced Repetition Improves Memory.” |
| Journal title | Italicized, title case. | Italicized, title case. | Italicized, title case. |
| Volume & issue | Volume italicized. Issue in parentheses: 15(3), 100–120. | Volume.number or volume number: 15.3, 100–120. | Volume, no issue number shown in parentheses. |
| Page ranges | P-numbers: p. 45 or pp. 45–50 in in-text citations. | Footnote uses “p.” or “pp.” Bibliography omits it. | “pp.” used in parentheses for direct quotes. |
| DOI format | https://doi.org/10.xxxx/xxxx |
https://doi.org/10.xxxx/xxxx |
https://doi.org/10.xxxx/xxxx |
Source Type 3: Website
| Formatting Dimension | APA 7th Edition | Chicago 18th Edition (Notes-Bibliography) | Chicago 18th Edition (Author-Date) |
|---|---|---|---|
| In-text citation | (National Institute of Mental Health, 2024) | Superscript number → footnote with full citation | (National Institute of Mental Health 2024) |
| Reference entry | Organization name. (2024, Month Day). Page title. URL | Organization name. Page Title. Full URL. Date accessed if relevant. | Organization name. Year. Page Title. Full URL. |
| Date placement | Year in parentheses after author. Full date (Month Day, Year) in reference list. | Full date in footnote. No separate year in parenthetical. | Year only, placed after author. |
| Retrieved / accessed date | Only if content changes over time (e.g., live charts, wikis). | “Accessed” date recommended for websites without clear update dates. | Not required, but “Accessed” can be added. |
Source Type 4: Book Chapter (Edited Volume)
| Formatting Dimension | APA 7th Edition | Chicago 18th Edition (Notes-Bibliography) | Chicago 18th Edition (Author-Date) |
|---|---|---|---|
| In-text citation | (Miller, 2023, as cited in Thompson, 2024) | Superscript → footnote with chapter title and page range | (Miller 2023) |
| Chapter title | Sentence case. In quotes within the reference entry. | Title case. Chapter title comes before book title. | Title case. Chapter title before book title. |
| Chapter page range | Included in reference entry: pp. 45–67. | No chapter page range in bibliography (2024 update). Only in footnotes. | Page range included in parentheses for direct quotes. |
| Bibliography vs. Footnote distinction | No footnotes — only the reference list. | Full citation in footnote; abbreviated form in subsequent footnotes. | No footnotes — only the reference list. |
When to Use APA vs Chicago: Discipline Mapping
You don’t choose a citation style — your professor, journal, or discipline chooses it for you. Here’s a quick-reference guide for which style belongs where:
| Discipline | Preferred Style | Why This Style Fits |
|---|---|---|
| Psychology, Education, Nursing | APA | The (author, year) format emphasizes recent research. Social sciences move fast — showing the year upfront helps readers judge relevance. |
| Sociology, Political Science, Business | APA or Chicago AD | Both fields sometimes use APA. Business journals often prefer APA for consistency with behavioral research. |
| History, Humanities, Theology | Chicago Notes-Bibliography | Footnotes allow scholars to add commentary, context, and methodological notes alongside the citation — something APA does not support. |
| Art History, Literature, Philosophy | Chicago Notes-Bibliography | Long-form analysis needs the flexibility that footnotes provide. The NB system is the default. |
| Physical Sciences, Natural Sciences | Chicago Author-Date | The AD system works well when year is important for context, but the NB system is also common in some science journals. |
When to choose Chicago NB vs Chicago AD:
- Notes-Bibliography → your assignment requires footnotes or endnotes. History papers almost always.
- Author-Date → your professor asked for author-year format. Common in sciences and social sciences that prefer Chicago over APA.
What we recommend: Always check your assignment guidelines first. If your professor doesn’t specify, ask — the wrong style can cost you formatting points even if your citations are accurate.
Chicago 18th Edition: What’s New (2024)
Chicago 18th edition, released in September 2024, is the first major update in over a decade. Here are the changes students should know about:
1. No place of publication required
Chicago 18th removed the city and publisher location from book citations. You no longer need “Chicago: University Press, 2024.” Just “University Press, 2024” is sufficient. This was one of the biggest simplifications in the edition.
2. Chapter page ranges removed from bibliography
In the bibliography, chapter page ranges are no longer included. They only appear in footnotes. This change makes bibliographic entries cleaner and reduces inconsistency across entries.
3. Digital source guidance
The 18th edition updated how to cite digital and online sources — including databases, websites, and social media. The rules now reflect how scholars actually access and cite material from digital platforms.
4. AI and generative content
Like APA 7th and MLA 9th, Chicago 18th edition now includes guidance for citing AI-generated content. If you use ChatGPT, Gemini, or similar tools as a source, the style guide provides specific citation formats.
5. Inclusive language updates
The 18th edition refined language guidelines to promote more inclusive terminology across citations and references. This is especially relevant for researchers working with diverse populations.
Why this matters for your paper: Most student guides still reflect the 17th edition or earlier. If your professor expects the 18th edition, you want to make sure your formatting matches — not an outdated version. Our Chicago style guide covers the basics, though it hasn’t been updated to reflect 18th edition changes yet.
APA 7th Edition: What Students Should Know
APA 7th edition (released 2020) has been stable for six years. Unlike Chicago 18th, APA hasn’t had a major public update since then — so most of what you learn in APA 7th is current. Here are the most relevant rules for students:
1. et al. starts at the first citation
If a source has three or more authors, use “et al.” from the first citation, not just the second. This was a change from APA 6th edition and it’s the single most common formatting mistake students make.
Click to expand — correct formatting example
Wrong (old APA 6th rule): First citation: (Smith, Jones, & Lee, 2024). Second citation: (Smith et al., 2024)
Right (APA 7th rule): First citation: (Smith et al., 2024). Second citation: (Smith et al., 2024)
2. DOI as full URL
Format DOI links as full URLs: https://doi.org/10.xxxx/xxxx. Don’t use “doi:” prefix or the old DOI format.
3. Up to 20 authors in reference list
List up to 20 authors’ names before using an ellipsis (…) for the rest. Only use “et al.” in the in-text citation when there are 3+ authors (from the first citation).
4. Title page matters
APA requires a separate title page with title, author, institution, course, instructor, and date. This is different from Chicago’s simple one-line title page.
For a complete list of APA 7th rules and examples, our APA 7th edition citation guide covers every source type with real examples.
MLA vs APA vs Chicago: Quick Context
MLA (Modern Language Association) is the third major citation style most students encounter. It’s primarily used in literature, arts, and humanities — overlapping partially with Chicago Notes-Bibliography.
For students who need MLA context:
- MLA (9th edition) uses “Works Cited” (not “References” or “Bibliography”) and parenthetical citations like
(Smith 45)— page number instead of year. - MLA doesn’t use footnotes for citations; it relies on parenthetical references.
- MLA title capitalization is different from both APA and Chicago.
The MLA Citation Style Complete Guide covers MLA in detail. If you’re working on a humanities paper, you’ll likely choose between MLA and Chicago NB — not between all three.
Citation Management Tools
No matter which style you use, the easiest way to avoid formatting errors is to use a citation manager:
- Zotero — Free, open-source. Supports APA, Chicago, MLA, and 10,000+ other styles. Great for students.
- Mendeley — Free. Strong reference library features. Popular in sciences.
- EndNote — Paid, institutional license. Full-featured, widely used in graduate programs.
- Citation Machine / EasyBib — Web-based, free citation generators. Good for quick single citations.
Our citation management tools comparison walks through each tool, its strengths, and which one works best depending on your discipline and budget.
Summary: What to Do Next
Here’s the tl;dr takeaway:
- APA 7th = in-text (author, year) + “References” list + sentence case titles. Use it for social sciences, education, and health.
- Chicago 18th NB = footnotes/endnotes + “Bibliography” + title case titles. Use it for history, humanities, and the arts.
- Chicago 18th AD = in-text (author year) + “References” + title case titles. Used in sciences and some social sciences.
Your next steps:
- Check your assignment guidelines for the required style.
- Use the comparison chart above as a quick reference while you format.
- Run your citations through a citation manager (Zotero or Mendeley recommended) to catch formatting errors.
- If you’re working with multiple source types, check our APA in-text citation examples or our APA 7th edition guide for source-specific examples.
Still unsure which style to use? Ask your professor. When in doubt, the style your department uses is the right one — not the one you prefer.