Capitalization rules can be tricky, but they're crucial for clear writing. From proper nouns to titles, knowing when to use uppercase letters helps you distinguish specific people, places, and things from general categories.
Sentence structure, formatting, and academic references also have their own capitalization quirks. Understanding these rules ensures your writing looks polished and professional, whether you're crafting an essay or sending an important email.
Proper Nouns and Titles
Capitalizing Names and Titles
The core principle here is simple: capitalize words that refer to specific people, places, or things. Keep things lowercase when you're talking about a general category.
- Personal names capitalize both first and last names (John Smith, Marie Curie).
- Titles of people capitalize when used as part of a name or as a direct address: President Lincoln, Doctor Jones, Thank you, Professor.
- When a title is used generically or descriptively, keep it lowercase: the president spoke, she visited a doctor.
- Geographic names capitalize all significant words (Rocky Mountains, Pacific Ocean, Lake Michigan).
- Organizations, institutions, and businesses capitalize main words (United Nations, Harvard University, the Red Cross).
The title rule trips people up most often. A good test: if you can replace the title with the person's name and the sentence still works, capitalize it. "I spoke with Professor Hernandez" → "I spoke with Maria." That works, so Professor is capitalized. But "She wants to become a professor" is general, so it stays lowercase.
Formatting Titles of Works and Trade Names
Titles of books, articles, films, and other works follow a specific pattern:
- Capitalize the first word and the last word, no matter what.
- Capitalize all principal words (nouns, verbs, adjectives, adverbs).
- Leave articles (a, an, the), coordinating conjunctions (and, but, or), and short prepositions (in, of, at, to) lowercase, unless they're the first or last word.
- Capitalize the first word after a colon in a title: The Great Gatsby: A Study in Symbolism.
For trade and brand names, always capitalize as the company does. Coca-Cola and Microsoft Word follow standard capitalization, but some brands use intentional lowercase styling, like iPhone and eBay. Follow the company's own formatting in those cases.
Acronyms and Initialisms
Both acronyms and initialisms are formed from the first letters of a phrase, but they differ in how you say them:
- Acronyms are pronounced as words and capitalize all letters: NASA, UNESCO, NAFTA.
- Initialisms are pronounced letter by letter and also capitalize all letters: FBI, CIA, ATM.
- Some acronyms have become so common that they're now treated as regular lowercase words: laser (light amplification by stimulated emission of radiation), scuba (self-contained underwater breathing apparatus).
When you write out the full phrase behind an acronym, only capitalize it if it's a proper noun. So you'd write "gross domestic product (GDP)" in lowercase, but "North Atlantic Treaty Organization (NATO)" capitalized, because it's the name of a specific organization.
Sentence Structure and Formatting
Beginning Sentences and Quotations
- Capitalize the first word of every sentence, including sentences within quotations.
- In dialogue, capitalize the first word of each speaker's quote: He said, "The weather is lovely today."
- After a colon, capitalize the first word only if what follows is a complete sentence. Compare: She had one goal: victory (fragment, lowercase) vs. She had one goal: She wanted to win the race (complete sentence, capitalized).
- For a complete sentence inside parentheses that stands alone, capitalize the first word and place the period inside: We arrived late. (The traffic was terrible.) But if the parenthetical sits inside another sentence, don't capitalize or add a final period: We arrived late (the traffic was terrible).
Formatting Dates and Time Periods
Days and months are treated as proper nouns, but seasons are not. This is one of the most commonly tested distinctions.
- Capitalize days of the week and months (Monday, April, November).
- Keep seasons lowercase unless they're part of a proper name: spring, winter, but Fall Semester 2024 or Winter Olympics.
- Holidays and special observances capitalize significant words (New Year's Day, Fourth of July, Veterans Day).
- Historical eras and periods capitalize (the Middle Ages, the Renaissance, the Gilded Age).
- Time zone abbreviations capitalize (EST, PST), but the spelled-out forms are lowercase (eastern standard time, pacific standard time).
Geographic and Directional Capitalization
The key distinction is between a region and a direction. Regions are proper nouns; directions are not.
- Capitalize when referring to a recognized region: the Midwest, the South, the Middle East.
- Keep it lowercase when indicating general direction: drive north on the highway, the wind blew east.
- Capitalize directional words that are part of a proper name: North Dakota, South Korea, West Virginia.
- Capitalize unique geographical features: Grand Canyon, Mount Everest, the Great Barrier Reef.
- Keep general geographic terms lowercase (the mountain, the river) unless they're part of a proper name (the Mississippi River, the Sahara Desert).
Academic and Historical References
Language and Cultural Capitalization
- Languages always capitalize: English, Spanish, Mandarin, Arabic.
- Nationalities and ethnic groups capitalize: French, Native American, Asian, Latino.
- Religious terms capitalize names of deities, holy books, and specific denominations: God, the Bible, the Quran, Buddhism, Catholicism.
- Use lowercase for general religious references that don't point to a specific entity: The ancient Greeks worshipped many gods; She treated the handbook like a bible.
- Cultural movements capitalize when they refer to specific recognized periods or styles: Romanticism, Art Deco, the Harlem Renaissance. Keep them lowercase when used in a general sense: She had a romantic view of the world.
Academic Disciplines and Courses
This area has a clear pattern that's easy to remember once you see it:
- General academic subjects stay lowercase: math, science, history, psychology.
- Languages are always capitalized, even as subjects: English, French, Latin.
- Specific course titles capitalize all significant words: Introduction to Psychology, Advanced Organic Chemistry, German 101.
- Degrees stay lowercase when referred to generically: a bachelor's degree, a master's in business administration.
- Capitalize the full formal name of a degree: Bachelor of Arts, Master of Science in Engineering.
The simplest way to remember: if it sounds like a course listing in a catalog, capitalize it. If it sounds like a casual mention of a subject area, keep it lowercase. "She studied history" vs. "She enrolled in History 201."
Historical Periods and Events
- Specific historical periods capitalize: the Renaissance, the Enlightenment, the Industrial Revolution.
- Major historical events capitalize significant words: World War II, the French Revolution, the Great Depression.
- Geological periods and eras capitalize: Jurassic Period, Ice Age, Mesozoic Era.
- Centuries and decades stay lowercase: the eighteenth century, the roaring twenties, the mid-1800s.
- Historical documents and agreements capitalize: the Constitution, the Treaty of Versailles, the Magna Carta, the Declaration of Independence.