Capitalization is considered neither punctuation nor grammar. It’s part of the mechanics of writing: spelling. With just as many confounding rules and exceptions as punctuation and grammar, capitalization guidelines are nevertheless intended to help you better express yourself.

No set of rules for capitalization existed in English until the eighteenth century. And even today your confidence may sometimes waver on what to make UPPERCASE or lowercase.

Let’s start with the easy rules—or semi-easy.

Capital letters signal the beginning of a new sentence

Sentences should start with a capital letter:
I did it right there.
And I did it again.

Capitalize “I” as a pronoun:

I think, therefore I am.

English is the only language that capitalizes the personal pronoun “I.” Why? It has something to do with Middle English distinguishing itself from the German word ich. In other words, rules can be arbitrary. Yeah, we know.  

In a title or a headline, capitalize to show the important words

The Importance of Being Earnest (play)
“How to Write a Great Sex Scene” (article or Internet post)
Headless Body in Topless Bar (New York Post headline)

When writing headlines or the titles of books and articles, capitalize the first and last words of the title. Also, proper nouns, pronouns, verbs, adjectives, and adverbs. Remember: just because a word in a headline is short, doesn’t mean it is necessarily lowercase. Articles, conjunctions, and prepositions should not be capitalized. 

Or you can always use an AI tool to capitalize your title correctly.

Capitalize proper nouns: names, places, companies, organizations, book titles, films, songs, and other media

Based in Connecticut, Talcott Notch is a literary agency.
Paula Munier lives in a white house.
Home at Night is her most recent wonderful book.

Capitalize official titles

Official titles or job titles (like president or senator) should be capitalized if they come before a name. The job itself is not capitalized.
President Biden lives in the White House.
Joe Biden, the president, lives in the White House.

Even so, erroneous uppercase-ness like “Biden is the President” and “Charles is the King” are not uncommon, and some guides suggest that fancy VIP positions automatically deserve capital letters. But this is correct:
Charles is the king of England.
King Charles III rules England.
A dogcatcher lives down the street.

Also capitalize a title when it’s part of a direct address:
“Was I speeding, Officer?”

Capitalize specific events and specific periods

Sorry, but this is another area that gets confusing. Time periods and events are capitalized when they refer to specific periods—basically, when they are proper nouns
On Boxing Day, I went boxing.

That said, general time periods are not capitalized unless they’re referred to by a specific name, and by that I mean a proper noun. So “the nineteenth century” is not capitalized because it’s a measure of time and not a proper noun, but…
the Roaring Twenties
the Ides of March

Ditto with historical events. Capitalize only what is specific
the American Civil War
a civil war in Spain

…though the names of historic eras are lowercase:
Elizabethan era

Shall we go north, South, east, or West?

Again, if we’re describing a specific place—for example, the South, you capitalize.

Down South is capitalized. If you are headed south, it’s lowercase. The people who live in a specific region are capitalized: Midwesterners, Northerners, etc. But when directions go before a place name, they are descriptive and usually not capitalized:
They love northern Wisconsin.

Sometimes the direction is part of the name—it’s a proper noun—so it is capitalized.
South Sudan
West Virginia

Capitalize proper nouns in family relationships

Writers, take note. In many manuscripts I find this done exactly wrong. If identifying a specific person, capitalize:
I love Grandma.
You must meet Aunt Dee.

When conveying that person’s relationship to the subject, use lowercase:
He owes your grandma money.
She looks like my aunt Dee.

YES: I can’t believe Mom let you wear that!
YES: His dad will be really bummed.
YES: “But Aunt June,” she begged, “Lars’s aunt said he could go.”

Capitalize months, holidays, days

These proper nouns should be capitalized:
Her birthday is February 29, which is Leap Day.

However, you should not capitalize the names of seasons, which are not categorized as proper nouns:
This spring, we’re hoping for a large turnout at the Career Authors Writers’ Retreat.

Capitalize Brand Names

Trademarked names are usually regarded as proper nouns.

So there’s Kleenex, Scotch Tape, and Xerox. But not so fast! Rules change when ubiquitous descriptive words lose their trademark (Realtor, Dumpster) and are downgraded to lower case (realtor, dumpster).

When in doubt, how to tell the difference? Google it.

Do not capitalize the word following a semicolon or colon

The curtain pulled shut; he saw no more.
The doctor told me what to focus on: colon health.

However, if a complete sentence follows a colon, it should be capitalized:
I would like to add to Margaret Atwood’s famous statement: It can’t be just any word—it has to be the right one.
The defining feature of New York City winters was freezing rain: He missed snow.

Common mistakes

  • The word medieval is lowercase. It is descriptive, not a proper noun.
  • The word “god” should be capitalized if it is being used as a proper name of a monotheistic god—as in God in Christianity and Judaism. Otherwise, the word should be lowercased, as in “the god of war.”
  • Likewise, capitalize “bible” if it is being used as the proper name of a religious book, as in the Christian Bible. Used as a general term, do not capitalize: “She considered The Chicago Manual of Style her bible.”
  • Check out official titles: Not The New York Times, but the New York Times—but The Washington Post! That’s its official title, with “The”—not the Washington Post.
  • It’s Twenty-First Street, not Twenty-first Street 

Capital Letter Abuse

For added emphasis or to express themselves emotionally, some writers give in to the urge to use ALL CAPS. Publishers may allow this stylistic excess, but that doesn’t make it right
“WHAT ARE YOU DOING?” I screamed.
But she’d promised me that SHE WOULD NOT TELL ANYONE!

Purists are offended. Well, maybe because it’s wrong. (Here’s a hilarious post on ALL CAPS netiquette.)

Also, I regularly come across certain passages—or gripped-teeth dialogue—broken up into separate sentences that are then capitalized
Never. Again.
“Do. It. Now!” he shouted.

Never again.
“Don’t do it!” I shouted.

It’s not too late. Do the right thing: punctuate and spell to impress.

What words do you think should or should not be capitalized? What mistakes do you regularly spot? Share with us on Facebook.