How to Use Acronyms

Anyone who’s read a text or perused social media has probably seen an acronym—a word made out of the first letters of each word in a phrase. But before there was LOL and OMG, there was SPQR (Senatus Populusque Romanus, “the senate and people of Rome”), radar (radio detection and ranging), and AWOL (absent without leave).

Some dictionaries insist that only an abbreviation pronounced as a word (e.g., NASA) can be called an acronym; if it’s pronounced as letters (e.g., UFO), it’s called an initialism. However, many people use acronym as a catch-all term for both types of abbreviation.

Punctuation

Before you start throwing acronyms around in your writing, you have to decide whether or not you’re going to use periods. USA or U.S.A.? VIP or V.I.P.? Acronyms with periods used to be more common, but today most style guides, including The Chicago Manual of Style, prefer them without.

Some editors will use periods in geographical acronyms like P.E.I. and U.S.S.R. but leave them out of words like DNA and TV. The New York Times Manual of Style and Usage puts periods in initialisms (H.I.V.) but not acronyms (AIDS). The easiest way to resolve this issue is to pick a dictionary you like and follow its practice.

Capitalization

Some acronyms start life as all capital letters and then, after repeated use, become lowercase. For example, laser (light amplification by the stimulated emission of radiation), scuba (self-contained underwater breathing apparatus), and sonar (sound navigation and ranging) have in the past been written in all capitals, but today they’re treated as regular, lowercase words.

Many British newspapers use all capital letters for initialisms (BBC) but only capitalize the first letter of acronyms (Gif). The New York Times Manual uses all caps for acronyms only if they’re under five letters—so they would write NATO but also Nafta. Personally, I find these rules unnecessarily complicated, and most style guides tend to agree, recommending all caps for both initialisms and acronyms. Again, consult your favourite dictionary if you’re not sure.

No matter how the acronym itself is capitalized, you never need to capitalize the words that create it (unless, of course, they’re words that normally use a capital, like the name of an organization). For example, BA is written out as bachelor’s degree, and HIV stands for human immunodeficiency virus.

• From ages four to six, Nergüi lived almost exclusively on PB&J—Peanut Butter and Jelly sandwiches. X
• From ages four to six, Nergüi lived almost exclusively on PB&J—peanut butter and jelly sandwiches. ✓
• No stranger to fanfiction, Zodwa had yet to dip her toe in the waters of Real Person Fic, known as RPF. X
• No stranger to fanfiction, Zodwa had yet to dip her toe in the waters of “real person fic,” known as RPF. ✓
• Brian’s friends in the PFJ (the People’s Front of Judea) despised the JPF (the Judean People’s Front). ✓

On the other hand, unconventional capitalization is often used for humour. For example, in A. A. Milne’s stories, Winnie-the-Pooh calls himself “a Bear of Very Little Brain.” If you’re capitalizing words for a specific effect—humorous or otherwise—rather than because they happen to make up an acronym, go right ahead.

• In the swamp they were beset by Rodents of Unusual Size, a.k.a. ROUS. 
• As punishment, the kids were forced to put away their phones and spend the rest of the road trip listening to LMM, or Lame Mom Music, which was surpassed in awfulness only by LDM, Lame Dad Music.

AM and PM

AM and PM stand for ante meridiem (Latin for “before noon”) and post meridiem (“after noon”). Chicago prefers lowercase letters with periods—6:00 a.m., 7:15 p.m.—but many people use capitals instead, usually without the periods: 6:00 AM, 7:15 PM. Often the abbreviations are written in small caps (this is easy to approximate in Word but may be tricky in other programs or on the web).

• No fan of the early bird, Lucifer set his alarm for 11:59 a.m.

BC and AD

Historical years may be written with the abbreviations BC (before Christ) or AD (anno Domini, Latin for “in the year of the Lord”), or with the less religious BCE (before the common era) or CE (common era). These can also be written with periods, or in small caps. Note that AD goes before the year.

• The Library of Alexandria is said to have burned down in 48 BC.
• After seven years as regent, Hatshepsut declared herself pharaoh around 1472 BCE.
• In AD 800, Charlemagne was crowned Holy Roman Emperor by the pope.
• Wu Zetian (624–705 CE) was the only empress to rule China in her own right.

OK and Okay

The word OK has been with us since at least 1839, when it was apparently an abbreviation for oll korrect (a joke spelling of all correct by nineteenth-century wags). Since its early days, OK has also been written okay. Both spellings are widely accepted; just be sure you stick to one throughout your document. Ok, on the other hand, is never okay in professional writing.

• “Ok,” said Koharu. “Now you’re gonna get it!” X
• “OK,” said Koharu. “Now you’re gonna get it” ✓
• “Okay,” said Koharu. “Now you’re gonna get it” ✓

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How to Capitalize Titles

The rules for capitalizing titles are collectively known as headline style, which is used not only for titles of works (books, movies, songs, etc.) but also for headlines and subheadings. Mastering this style isn’t so much a matter of learning what words to capitalize as learning what words not to capitalize.

Flying Monsters: A History

Headline Style: The Basics

Not all publications use headline style; some use sentence style, in which only the first letter is capitalized. Others say “the hell with it” and capitalize every single word, no matter what it is (Buzzfeed, I’m looking at you). But most editors follow the rules laid out in The Chicago Manual of Style.

Chicago recommends capitalizing all the important words: nouns, verbs, pronouns, adjectives, and adverbs. They also capitalize the first and last words of both title and subtitle. 

• Flying Monsters: A History

What Not to Capitalize in Headline Style

• Articles—the, a, and an—should be lowercase. Unless, of course, they’re the first or last words of the title or subtitle, like A in the example above.

• Chicago uses lowercase for all prepositions, no matter how long; however, many editors capitalize prepositions of more than a certain number of letters.

• Conjunctions, such as and, but, or, and nor, are lowercase.

• To is lowercase when it’s part of an infinitive verb (How to Twerk).

• As is always lowercase.

• Bits of foreign names like de and von, if they’re lowercase in the original spelling, are lowercase in titles (The von Trapp Family Singers).

Unconscious Robber Comes To and Flees

When to Capitalize Prepositions

Here’s where it gets tricky: the same word can perform different roles, some of which are capitalized and some of which are not. To, for example, can be a preposition (Come to Our Krampus Party!), part of an infinitive (I Have Come to Mourn My Wasted Youth), or part of a phrasal verb (Unconscious Robber Comes To and Flees).

Phrasal verbs (like come to) happen when a verb + preposition(s) forms a kind of unit, one whose meaning is distinct from what its words mean separately. Other examples of phrasal verbs are turn down, put off, hang out, put up with, and sit in for. These prepositions have been transmogrified into (parts of) verbs, so they get capitalized in headline style.

• Timothy Leary titled his spoken-word album Turn On, Tune In, Drop Out.
• In Bringing Up Baby, Cary Grant dons a negligee.

Prepositions are also capitalized when they serve as adjectives.

• Push the On Button
• No Running up the Down Escalator

Prepositions in Latin phrases like in vitro and per capita are treated the same as English prepositions: they’re lowercase except when the phrase functions as an adjective or adverb.

• Fertilization in Vitro but About In Vitro Fertilization
• Clowns per Capita but Measuring Per Capita Clownage

Participles, you may recall, are verb forms ending in –ing or –ed. Some of them may act as prepositions, such as including, regarding, given, and based on. In that case, Chicago doesn’t capitalize them.

• Four Theories concerning the Gospel according to Matthew

However, lots of editors think this looks clunky and choose to capitalize prepositions over a certain number of letters (usually three or four). This policy has the bonus of cutting down the number of words you need to agonize over. Is around being an adverb or a preposition? Who cares! It’s six letters, so cap that puppy!

• Four Theories Concerning the Gospel According to Matthew
• Haberdashery Around the World

Haberdashery Around the World

When a Conjunction Is Not a Conjunction

Conjunctions, as you might remember, join two clauses to form a sentence. So and yet are conjunctions—except when they’re adverbs.

• Darkness Has Prevailed, yet All Is Not Lost but We Have Not Yet Begun to Fight
• You’re Annoying so I Left but You’re So Vain

Whenever a word is being discussed as a word, it’s functioning as a noun, and is therefore capitalized.

• On the Abbreviations of “And” and “In” in Text Messages
• No Ifs, Ands, or Buts!

Capitalizing Hyphenated Words

Should you capitalize both words in half-baked? What about post-coital?

Chicago capitalizes both parts of compound words, except when the first part is only a prefix—something that can’t stand alone—in which case the second part is lowercase.

• Half-Baked Brownies: Cooking with Low-THC Marijuana
• Le Petit Mort: A Study of Post-coital Lassitude
• Hacking Government E-mails for Fun and Profit

Other publications capitalize only the first part of a compound—except, obviously, in the case of proper nouns (Ali, French, Google), which are always capitalized.

• Half-baked Brownies: Cooking with Low-THC Marijuana
• An Exhibition of Anti-Soviet Propaganda from World War II
• Post-Freudian Dream Interpretation

If a hyphenated phrase contains a word that would normally be lowercase, like an article or a preposition, keep it lowercase.

• The Out-of-Work Actors’ Fund
• Dyed-in-the-Wool Marxist Refuses Knighthood

Post-Freudian Dream Interpretation

Knowing headline style isn’t useful only for bibliographers; it’s an indispensable skill for any writer. You need it to write the name of your favourite song (“These Boots Are Made for Walkin’ ”), the TV show you’re currently obsessed with (Game of Thrones), or the work of art that best sums up this year (Edvard Munch’s The Scream). You’ll probably use it in the titles of your blog posts and the subheadings on your website (see above). And you’ll find it handy should you ever need to quote a sign (Beware of Dog) or a motto (Keep Calm and Carry On). Headline style’s somewhat arbitrary rules may vary, but be consistent and you won’t go wrong.

Capitalization, Honorifics, and Yo’ Mama

If you tell your GP, “Give it to me straight, doctor,” does she deserve a capital letter? Should it be “Give it to me straight, Doctor”? It depends who you ask. When it comes to capitalizing titles like professor or miss (also called honorifics), there is dissension in the ranks of grammarians.

"Dammit, Jim, I'm a doctor, not a sushi chef!"

Direct Address

• “Dammit, Jim, I’m a doctor, not a sushi chef!” protested Doctor McCoy.

We can all agree that doctor should be lowercase here and Doctor McCoy should be capitalized. The first is simply an ordinary noun and needs no special treatment: a doctor, the doctor, my doctor. The second is an honorific in front of a name, and as with Captain Kirk, Mr. Sulu, or Lieutenant Uhura, it should be capitalized.

Things get more contentious when the honorific steps into the shoes of a name. Dr. McCoy’s dialogue is an example of direct address (also called the vocative case): he’s speaking to someone—Kirk—directly. When he says “Dammit, Jim,” the use of a capital for Jim is obvious; it’s a name. But what if McCoy were addressing him as captain? What about buster?

• “Dammit, C/captain, I’m a doctor, not a trapeze artist!”
• “I’ll darn well sass you if I feel like it, b/Buster!”

Up Style vs. Down Style

The Chicago Manual of Style, the bible of copy editors, is firm on the use of capitals in direct address. In an online Q & A column, Chicago’s editors write, “It doesn’t matter what the word is: captain, coach, aunt, joker, brain. If it’s used in place of a name, cap it.”

• “Dammit, Captain, I’m a doctor, not a trapeze artist!”
• “I’ll darn well sass you if I feel like it, Buster!”

On the other hand, well-known grammar arbiter Grammar Girl writes, “In cases where [honorifics] stand alone, even in direct address, they are lowercase.” She offers as examples “Hey, mister, look out for that pelican!” and “Gee, doctor, it hurts when I stick out my tongue.”

• “Dammit, captain, I’m a doctor, not a trapeze artist!”
• “I’ll darn well sass you if I feel like it, buster!”

The generous use of capitalization is sometimes referred to as up style, while using capitals more sparingly is called down style. Manuals like Chicago, which tend to embrace up style for direct address, are generally geared towards formal writing—say, for academic, government, or business contexts. Pick up any popular book, however, and you’ll most likely see down style.

But that doesn’t mean capitalizing honorifics is a matter of personal whim. There are a few words that even the most formal style guides won’t capitalize, and some words that fiction editors would wince to see in lowercase.

Do go haunt someone else, Mother!

Relativity: Family Titles

Mom (or Mum), Dad, Mother, and Father are always capitalized—when they’re used like names. Try substituting a name (we’ll use Spock) for the title in question. If it makes sense, cap it; if it doesn’t, use lowercase.

• My mom said she’d drive us to the rave. (my Spock X)
• Are you going to bake a file into Father’s cake? (Spock’s cake ✓)
• Do go haunt someone else, Mother! (haunt someone else, Spock ✓)
• All the dads are wearing tutus to the barbecue. (all the Spocks X)

You can apply the Spock method to other family members as well:

• Who gave Grandmother a litre of vodka? (who gave Spock ✓)
• Phoebe inherited the time travel machine from her grandpa. (her Spock X)
• One should not take advice from one’s disreputable uncle. (one’s Spock X)
• I already knew you were a witch, Auntie. (you were a witch, Spock ✓)
• Don’t let Uncle bring his Jello salad. (don’t let Spock ✓)

Of course, family titles are always capitalized when they’re followed by a name, in the same way you’d capitalize Doctor Zhivago or Captain America.

• our Grandma Eng (but our grandma, Eng)
• his Uncle Ahmed (but his uncle, Ahmed)
• Flora’s Cousin Judith (but Flora’s cousin, Judith)

Some family titles are less obviously capitalized. Brother or sister, for example, could mean any old schmo.

• Can you spare a dime, brother?
• You’re a tough cookie, sister.

Even when talking to your actual sibling, you might still prefer a more casual “Nice one, bro.” In some cultures titles like uncle and auntie are applied generally and not just to your parents’ siblings; an author might decide to convey this by keeping them lowercase.

You’re a tough cookie, sister.

Sir, Ma’am, and Nicknames

For reasons lost in the mists of time (or at least not immediately findable on the Internet), the following words are never capitalized when used without a name:

• sir
• ma’am / madam
• my lord
• my lady

(Hard-core grammar nerds can confirm this in section 8.32 of the Chicago Manual.) Even should you happen to speak to the Queen, she would only merit lowercase:

• “Your corgis are eating my shoe, ma’am.”

Nicknames, on the other hand, are always capitalized, since they’re another type of name—Bucky, Stretch, Chewy, Four-Eyes—but sometimes the line between a personal nickname and a generic descriptive term can get kind of fuzzy. Consider kiddo, genius, loser, killer, and sunshine. Of course, up style would cap these in any case (provided they were used in place of a name). If you’re using down style, you might want to think about the difference between a word that’s specific to an individual and one that’s used less discriminately. John Henry Holliday was known as Doc at the O.K. Corral, but Bugs Bunny says “What’s up, doc?” to a variety of characters.

When to Capitalize Direct Address: The Takeaway

Those of you looking for hard and fast rules on this issue are doomed to disappointment. As with so many grammar questions, the answer boils down to context and consistency. What degree of formality does your reader expect—are you writing a business letter or a blog post? Once you’ve chosen your style—up or down—apply it consistently. Remember to capitalize Mom and Dad where appropriate (calling on Mr. Spock for help as needed), and leave sir and ma’am lowercase. After that, dear reader, you’re on your own.