Chicago Title Case Rules: Complete Guide to the 18th Edition
Learn current Chicago title case rules from the 18th edition, including prepositions, hyphenated compounds, subtitles, minor words, and examples.
Chicago title case changed in a way that many writers and older online converters still miss. The 18th edition of The Chicago Manual of Style, published in 2024, now capitalizes prepositions of five letters or more in titles. That update makes current Chicago title capitalization noticeably different from the older rule that lowercased prepositions regardless of length.
If you learned Chicago years ago, or if your favorite converter has not been updated, it is worth checking how it handles words such as “About,” “Between,” and “Through.”
What Is Chicago Title Case?
Chicago title case is a system for capitalizing English language titles and headings. It generally capitalizes the first word, last word, and major words. Articles, coordinating conjunctions, and shorter prepositions are usually lowercase in the middle unless a position based rule requires a capital.
Example:
A Guide to Writing About Modern Publishing
The small word “to” stays lowercase, while “About” is capitalized under Chicago 18 because it is a preposition with five or more letters.
The Biggest Chicago 18 Change for Titles
Older Chicago editions instructed writers to lowercase prepositions in titles regardless of length.
Chicago 18 changed that approach.
Current rule:
Prepositions of five letters or more are capitalized in titles.
Examples:
About
Above
Across
After
Along
Among
Around
Before
Behind
Below
Beneath
Beside
Between
Beyond
During
Inside
Outside
Through
Toward
Underneath
Within
Not every word in this list functions as a preposition in every sentence, but the length rule matters when it does.
Shorter prepositions such as “at,” “by,” “for,” “from,” “in,” “of,” “on,” and “to” generally remain lowercase in the middle of a title.
Major Words in Chicago Title Case
Chicago capitalizes major words such as:
- Nouns
- Pronouns
- Verbs
- Adjectives
- Adverbs
- Subordinating conjunctions
- Other words treated as major under the style
Example:
Why Writers Choose Clear Language
“Why,” “Writers,” “Choose,” “Clear,” and “Language” are all treated as major.
Articles in Chicago Titles
The articles “a,” “an,” and “the” are generally lowercase in the middle of a Chicago style title.
Example:
Writing for the Modern Reader
However, the first word of a title is capitalized:
The Modern Reader's Guide to Editing
The first word of a subtitle is also capitalized even when it is an article:
Editing for Everyone: A Practical Introduction
Position overrides the normal lowercase treatment.
Coordinating Conjunctions
Common coordinating conjunctions such as “and,” “but,” “for,” “or,” and “nor” are normally lowercase in the middle.
Example:
Writing and Editing for Books
The conjunction “and” remains lowercase.
Do not use a word list blindly. A word can perform different grammatical functions in different sentences, and style rules sometimes depend on function.
The Infinitive “to”
Chicago traditionally lowercases “to” when it is part of an infinitive.
Example:
How to Write a Better Introduction
The word “to” is lowercase.
This is one place where blindly capitalizing every word can produce a result that looks more like proper case than Chicago title case.
First and Last Words
Chicago capitalizes the first and last word of a title or subtitle.
This can override an ordinary minor word rule.
Example:
What We Are Working For
“For” is the last word, so it is capitalized.
That is why title capitalization cannot be handled accurately by checking only whether a word appears on a lowercase list.
Subtitles
A subtitle usually begins after punctuation such as a colon.
Example:
The Craft of Editing: A Guide for New Writers
“A” is capitalized because it starts the subtitle.
The rest of the subtitle follows normal Chicago title case rules.
Hyphenated Compounds in Chicago 18
The 18th edition also revised title treatment for some hyphenated terms. In particular, later elements of a hyphenated term that begins with a prefix are capitalized according to the general title capitalization rule.
An example discussed in Chicago's update material is:
Anti-Intellectual Pursuits
Older style could produce different treatment for the second element in some prefixed compounds.
Hyphenated titles can be complicated because the word relationship matters. A good converter should use current rules, but a professional editor should still verify unusual compounds.
Phrasal Verbs
Phrasal verbs deserve special attention because a short word can be part of the verb rather than functioning as an ordinary preposition.
Examples include combinations such as:
Bring Up
Give In
Turn Off
Depending on how the words function, a Chicago title may capitalize a particle that a simple preposition list would lowercase.
This is one reason pure word length algorithms are not enough for high quality title capitalization.
Chicago Title Case Examples
Input:
a room with a view
Chicago 18:
A Room with a View
“With” has four letters, so it remains lowercase.
Input:
much ado about nothing
Chicago 18:
Much Ado About Nothing
“About” has five letters, so it is capitalized under current Chicago guidance.
Input:
how to write about history
Chicago 18:
How to Write About History
“To” remains lowercase, while “About” is capitalized.
Chicago vs APA
APA capitalizes words of four letters or more in title case. Chicago 18 uses a five letter threshold for prepositions.
This can produce different results.
Example word:
with
APA may capitalize it:
Writing With Purpose
Chicago keeps it lowercase when it functions as a preposition:
Writing with Purpose
Word:
about
Both styles can capitalize it, but for different rule structures.
Chicago vs MLA
MLA generally lowercases prepositions in the middle of English titles regardless of length.
That means a title can differ clearly:
Chicago 18:
Thinking About Language
MLA:
Thinking about Language
Both can be correct within their own style.
Chicago vs AP
AP and APA capitalize words of four letters or more in composition titles, while Chicago's updated preposition threshold is five letters.
A word such as “with” is an easy test.
AP:
Working With Data
Chicago:
Working with Data
This small difference is exactly why users should choose the intended style rather than select generic Title Case.
Does Chicago Use Sentence Case?
Chicago supports both title case and sentence case depending on editorial context and house style. The 18th edition also updates terminology, referring to “title case” and “sentence case” rather than the older “headline style” and “sentence style” labels.
A publisher can choose sentence case for a particular context even when Chicago provides title case rules.
Common Chicago Capitalization Mistakes
Using an old preposition rule
If a converter lowercases “About,” “Between,” or “Through” simply because they are prepositions, it may be following older Chicago guidance.
Capitalizing “to” in every infinitive
Chicago generally keeps infinitive “to” lowercase.
Lowercasing the last word
The last word is capitalized even if it would usually be minor in the middle.
Treating every hyphen the same
Compound structure can affect capitalization.
Ignoring brand and proper name styling
Recognized names should keep their established capitalization.
How to Use CapitalizeText.live for Chicago Titles
Paste your title, select Chicago, and choose Title Case. The result should follow the current Chicago 18 rules implemented by the tool.
If you are comparing a title from an older manuscript, switch between styles and pay attention to longer prepositions and compounds. Those are likely places where old and current output can differ.
Related Resources
- Use the Title Case Converter
- APA Title Case vs Sentence Case: When Should You Use Each?
- APA vs MLA vs Chicago vs AP Title Capitalization: What Is the Difference?
Frequently Asked Questions
Does Chicago capitalize “About” in a title?
Yes under the 18th edition when “about” functions as a preposition in the title. Chicago now capitalizes prepositions of five letters or more.
Is “With” capitalized in Chicago title case?
Usually no when it functions as a preposition, because it has four letters.
Is “to” capitalized in an infinitive?
Chicago generally lowercases the infinitive “to.”
Did Chicago title case change in the 18th edition?
Yes. One important change is that prepositions of five letters or more are now capitalized. Chicago also updated guidance for certain hyphenated terms.