Understanding Chicago Manual of Style Title Capitalization
The Chicago Manual of Style (CMOS), now in its 17th edition, is one of the most widely used style guides for book publishing, academic writing, and professional communications. Its title capitalization rules strike a balance between readability and formality, making it ideal for books, articles, and formal publications.
Chicago Style Capitalization Rules
Chicago style follows a specific set of rules that differ slightly from both APA and MLA formats. Understanding these nuances is crucial for proper formatting.
Always Capitalize
- First and Last Words: Regardless of part of speech, always capitalize the first and last words of a title or subtitle
- Major Words: Capitalize all nouns, pronouns, adjectives, verbs, and adverbs
- Subordinating Conjunctions: Words like "although," "because," "if," "since," "unless," and "until" should be capitalized
- Words After Colons: Capitalize the first word after a colon in a title
Keep Lowercase
The following word types should remain lowercase (unless they're the first or last word):
- Articles: a, an, the
- Coordinating Conjunctions: and, but, for, nor, or, so, yet
- Prepositions: All prepositions regardless of length (at, by, for, from, in, into, of, on, to, with, etc.)
- The "to" in Infinitives: "to" before a verb stays lowercase
Chicago vs APA vs MLA: Key Differences
While all three major style guides share some common ground, their approaches to prepositions and minor words differ significantly:
| Style Guide | Preposition Rule | Example |
|---|---|---|
| Chicago | All prepositions lowercase (unless first/last) | "A Study of Climate Change" |
| APA | 4+ letter words capitalized | "A Study of Climate Change" (same result) |
| MLA | All principal words capitalized | "A Study of Climate Change" (same result) |
The key difference emerges with longer prepositions:
Title: "Looking through the Window"
- Chicago: "Looking through the Window" (through is lowercase)
- APA: "Looking Through the Window" (through has 7 letters)
- MLA: "Looking Through the Window" (principal word)
Special Cases in Chicago Style
Hyphenated Words
Chicago style has specific rules for hyphenated compounds:
- Capitalize both parts if they're equal: "Self-Control," "Twenty-First"
- Lowercase the second part if it's a particle or prefix: "E-commerce," "Anti-inflammatory"
- Exception: Always capitalize after a hyphen if it's the first word: "E-Commerce in Modern Society"
Subtitles After Colons
Unlike some other styles, Chicago always capitalizes the first word after a colon in titles:
Correct: "Technology in Education: The Digital Revolution"
Incorrect: "Technology in Education: the Digital Revolution"
Numbers and Acronyms
- Spell out numbers when possible: "Nineteen Eighty-Four" rather than "1984"
- Keep acronyms in all caps: "NASA," "FBI," "HTML"
- For technical acronyms at the start of titles, capitalize normally: "HTTP Protocol Basics"
When to Use Chicago Style
Chicago Manual of Style is the preferred format for:
- Book Publishing: Most trade and academic publishers follow Chicago style
- Historical Writing: History journals and publications predominantly use CMOS
- Arts and Humanities: Many fields outside of literature prefer Chicago over MLA
- Business Publications: Corporate reports, white papers, and professional communications
- Magazine and Newspaper Articles: Though some publications have house styles
Common Chicago Style Mistakes
Mistake #1: Capitalizing Short Prepositions
Many people incorrectly capitalize short prepositions thinking they follow APA's 4-letter rule.
❌ "The Effect Of Climate Change On Biodiversity"
✓ "The Effect of Climate Change on Biodiversity"
Mistake #2: Lowercase After Colons
Unlike APA, Chicago always capitalizes after a colon.
❌ "American History: the colonial period"
✓ "American History: The Colonial Period"
Mistake #3: Treating All Conjunctions the Same
Coordinating conjunctions (and, but, or) stay lowercase, but subordinating conjunctions (although, because, since) are capitalized.
❌ "What To Do When You're Lost"
✓ "What to Do When You're Lost"
Chicago Style in Practice: More Examples
Book Titles
- "The Catcher in the Rye"
- "One Hundred Years of Solitude"
- "A Brief History of Time"
- "The Hitchhiker's Guide to the Galaxy"
Article Titles
- "The Role of Artificial Intelligence in Modern Healthcare"
- "Climate Change: An Analysis of Current Trends"
- "Why Traditional Marketing No Longer Works"
- "Understanding the Basics of Quantum Computing"
Chapter Headings
- "Getting Started with Your First Project"
- "Best Practices for Team Collaboration"
- "Advanced Techniques in Data Analysis"
- "The Future of Renewable Energy"
Tips for Mastering Chicago Style
1. Focus on Word Function, Not Length: Unlike APA which uses word length, Chicago focuses on grammatical function. Ask yourself: Is this word a major word (noun, verb, adjective, adverb) or a minor word (article, preposition, coordinating conjunction)?
2. Remember the First/Last Rule: No matter what type of word it is, the first and last words are always capitalized. This includes articles and prepositions: "A Study of Mathematics in the Modern Era"
3. Use a Checklist: When formatting important titles, use this mental checklist:
- Is the first word capitalized? ✓
- Is the last word capitalized? ✓
- Are all nouns, pronouns, adjectives, verbs, and adverbs capitalized? ✓
- Are articles, prepositions, and coordinating conjunctions lowercase (except first/last)? ✓
- Is the word after a colon capitalized? ✓
4. Keep a Reference Handy: When in doubt, consult the Chicago Manual of Style or use this tool. It's better to verify than to guess.
Chicago Style and Digital Publishing
In the age of digital publishing, Chicago style remains relevant but has adapted to modern needs:
- URLs and Email: Keep original capitalization for web addresses and email addresses
- Hashtags: Capitalize each word in multi-word hashtags for readability: #ClimateChange
- File Names: While not strictly title case, many organizations use Chicago-style capitalization for file naming conventions
Frequently Asked Questions
Should I capitalize "with" in Chicago style?
No. "With" is a preposition and should remain lowercase unless it's the first or last word: "Gone with the Wind"
How do I handle a title that's all lowercase intentionally?
For artistic works with intentional lowercase styling (like bell hooks or e.e. cummings), follow the author's preference in your text but capitalize normally in your bibliography.
What about brand names with unusual capitalization?
Respect the brand's official capitalization: "iPhone," "eBay," "WordPerfect." However, if it starts a title, capitalize the first letter: "EBay's Business Model"
Do I use title case for all headings?
Chicago style recommends title case for major headings (chapter titles, main sections) but allows sentence case for subheadings. Follow your publisher's or organization's specific guidelines.
Converting from Other Styles
If you're transitioning from another style guide to Chicago:
- From APA: Review all 4+ letter prepositions and change to lowercase
- From MLA: The styles are very similar; main check is prepositions
- From AP Style: AP is more similar to APA; adjust prepositions accordingly