Professional organizations produce many types of written materials, and each document has different communication goals. A news release, annual report, research publication, grant proposal, and article may all require different approaches to grammar, punctuation, formatting, and style.
That’s why style guides matter.
Two of the most commonly used style guides in professional writing and editing are Associated Press (AP) Style and The Chicago Manual of Style (Chicago Style).
Both provide rules for consistency and clarity, but they’re designed for different types of writing.
Understanding the difference between AP Style and Chicago Style can help organizations choose the right approach for their documents and maintain a consistent professional voice.
What Is a Style Guide?
A style guide is a set of writing and formatting standards that helps organizations create consistent documents.
Style guides provide guidance on topics such as:
- Grammar
- Punctuation
- Capitalization
- Numbers
- Abbreviations
- Titles
- Dates
- Citations
- Formatting
Without a style guide, different writers may make different choices throughout a document, creating inconsistencies that can distract readers.
A professional editor uses style guides to ensure that documents follow established standards and communicate clearly.
What Is AP Style?
The Associated Press Stylebook, commonly called AP Style, is widely used in journalism, media, public relations, government communications, and organizations that create public-facing content.
AP Style focuses on writing that is:
- Clear
- Concise
- Accessible
- Easy to read
- Suitable for broad audiences
It’s especially common for documents designed to communicate quickly with the public.
Organizations that often use AP Style include:
- News organizations
- Nonprofits
- Government agencies
- Public relations teams
- Universities
- Marketing departments
What Is Chicago Style?
The Chicago Manual of Style, often called Chicago Style or CMS, is commonly used in publishing, academic writing, research, and longer-form professional documents.
Chicago Style provides detailed guidance on:
- Grammar
- Punctuation
- Citations
- Source documentation
- Manuscript preparation
- Publishing standards
It is often used for documents that require a higher level of editorial detail and formal structure.
Organizations that often use Chicago Style include:
- Publishers
- Academic institutions
- Researchers
- Authors
- Professional organizations producing long-form publications
Key Differences Between AP Style and Chicago Style
While both styles aim to improve consistency and readability, they approach certain writing decisions differently.
Commas
One of the most well-known differences involves the serial comma, also known as the Oxford comma.
AP Style:
AP Style generally does not use a comma before the final item in a simple list.
Example:
The program supports students, teachers and families.
Chicago Style:
Chicago Style typically uses the serial comma.
Example:
The program supports students, teachers, and families.
Neither approach is incorrect. The important thing is to choose one style and apply it consistently.
Numbers
AP Style and Chicago Style have different approaches to writing numbers.
AP Style:
AP Style generally spells out numbers one through nine and uses numerals for 10 and above.
Example:
The organization served five communities and provided services to 12,000 residents.
Chicago Style:
Chicago Style often spells out numbers one through 100 in formal writing, although there are exceptions.
Example:
The organization served five communities and provided services to twelve thousand residents.
The appropriate choice depends on the type of document and audience.
Titles and Job Descriptions
Both styles provide guidance on titles, but they may differ in formatting.
AP Style:
Job titles are usually capitalized only when they appear directly before a person’s name.
Example:
President Maria Lopez announced the initiative.
Maria Lopez, president of the organization, announced the initiative.
Chicago Style:
Chicago Style follows similar principles but provides more detailed guidance for formal publications.
A professional editor can help determine the best approach based on your document type.
Dates and Months
AP Style uses abbreviations for certain months when paired with a specific date.
Example:
Jan. 15, 2026
Chicago Style generally spells out months.
Example:
January 15, 2026
These small differences matter when creating polished, consistent documents.
Citations and References
One of the biggest differences between AP Style and Chicago Style involves citations.
AP Style is commonly used for shorter public-facing content where extensive citations may not be necessary.
Chicago Style provides detailed systems for:
- Notes and bibliography
- Footnotes
- Endnotes
- Source documentation
Academic, research, and publication-focused documents often require Chicago Style citation guidance.
Which Style Guide Should Your Organization Use?
The right style guide depends on your audience, purpose, and type of document.
AP Style May Be a Good Choice For:
- Press releases
- Newsletters
- Websites
- Public announcements
- Social media content
- Government communications
- Public-facing reports
Chicago Style May Be a Good Choice For:
- Books
- Research publications
- Academic documents
- Long-form reports
- Manuscripts
- Publications requiring detailed citations
Some organizations also create their own internal style guides that combine elements from multiple sources.
Why Style Consistency Matters
Readers may not notice when a document follows a style guide, but they often notice when it doesn’t.
Inconsistent writing can create confusion through differences in:
- Capitalization
- Numbers
- Punctuation
- Terminology
- Formatting
Consistency helps organizations appear professional and trustworthy.
How Professional Editing Helps
Choosing and applying a style guide can be challenging, especially for organizations producing complex documents with multiple contributors. Professional editors understand how to apply style guidelines while maintaining the organization’s voice and communication goals.
An editor can help review:
- Grammar and punctuation
- Style consistency
- Formatting choices
- Terminology
- Numbers and dates
- Document structure
Professional editing ensures that your documents follow appropriate standards while remaining clear and accessible to your audience.
At SP Editing, we help nonprofits, government agencies, educational institutions, healthcare organizations, foundations, and businesses create polished, consistent documents that communicate effectively.
Our editing services include support for:
- Annual reports
- Grant proposals
- Research publications
- Policy documents
- Financial communications
- Websites
- Public-facing materials
We work with organizations to apply the appropriate style standards, improve readability, and create documents that reflect professionalism and attention to detail.
Whether your organization follows AP Style, Chicago Style, or an internal style guide, SP Editing can help ensure your documents are clear, consistent, and ready for your audience.
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