Numbers, Abbreviations & Hyphens in Title Case
Updated September 2026 · 9 min read
Most title case questions are about ordinary words - is "to" capitalized, is "with" capitalized. But three categories break the normal rules entirely: numbers, abbreviations, and hyphenated compounds. None of them play by the "capitalize major words, lowercase minor words" logic that governs everything else, and getting them wrong is an easy way to make an otherwise correct headline look off. This page covers all three in one place.
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Numbers in Title Case
The first thing to understand about numbers is that numerals - the digits themselves, like 5 or 2026 - don't actually have a "case" to capitalize or lowercase. A "5" looks the same at the start of a title, the end, or buried in the middle. The real questions people run into are about ordinal suffixes, spelled-out numbers, and decades, all of which do have letters that can be styled correctly or incorrectly.
| Number Type | Rule | Example |
|---|---|---|
| Numerals (5, 10, 2026) | Numerals have no letter case, so they're never "capitalized" or "lowercased" - they're written the same everywhere in a title. | Top 10 Tips, Best Books of 2026 |
| Spelled-out numbers (One, Ten, Twenty) | Treated as ordinary major words (nouns or adjectives) and capitalized like any other significant word, regardless of length. | The Ten Commandments, Chapter One |
| Ordinal numerals (21st, 3rd) | Only the digits get any styling attention - the letter suffix (st, nd, rd, th) stays lowercase and is never capitalized on its own. | 21st Century, 3rd Edition (not 21St or 3Rd) |
| Spelled-out ordinals (Twenty-First, Third) | Capitalized like any major word - and if hyphenated, follow the hyphenation rule for that style guide. | Twenty-First Century, Third Time's the Charm |
| Decades (1990s, '90s) | The trailing "s" is lowercase; it's a plural marker, not a separate word. | The 1990s, Music of the '90s |
The most common mistake here is capitalizing an ordinal suffix - writing "21St Century" instead of "21st Century." The suffix isn't a separate word, so it never gets its own capital letter, no matter how confident your word processor's autocorrect is that it should.
Abbreviations & Acronyms
Abbreviations and acronyms are the second category that ignores the usual rules. A short preposition like "at" gets lowercased in the middle of a title because it's a minor word - but an abbreviation like "FBI" or "CEO" is short for entirely different reasons, and title case doesn't touch it. Abbreviations keep whatever capitalization pattern they already have, in any position in the title.
| Abbreviation Type | Rule | Example |
|---|---|---|
| Acronyms & initialisms (NASA, FBI, CEO, UK) | Keep the standard all-caps form no matter where the word falls in the title - the short-word lowercase rule for articles and prepositions does not apply to abbreviations. | How the FBI Investigates Cybercrime |
| Country/region abbreviations (U.S., UK, U.K.) | Keep the periods or lack of them exactly as your style guide prescribes (AP uses U.S. with periods; many web styles drop them to US) - never re-case the letters themselves. | U.S. Exports Rise in 2026 |
| Titles before a name (Mr., Dr., St.) | Always capitalized, just like they would be in running text - position in the title doesn't change this. | Dr. Smith's Guide to Better Sleep |
| Degree abbreviations (PhD, MBA, RN) | Keep the source capitalization pattern used by the degree-granting convention; don't lowercase any letters to match a "short word" rule. | Why Getting an MBA Still Pays Off |
| Time-of-day abbreviations (a.m., p.m.) | Most style guides keep these lowercase with periods even inside a title case headline, since they function as a fixed technical abbreviation rather than a normal word - avoid starting a title with one if you can. | Meetings Start at 9 a.m. Sharp |
| Versus (vs., v.) | Stays lowercase with its period, treated as a fixed abbreviation rather than capitalized or lowercased by the usual minor-word rules. | Title Case vs. Sentence Case |
Not sure how a specific word or abbreviation should land? Paste your title into our free tool and it applies each style guide's rules automatically - it won't accidentally lowercase an acronym just because it's short.
Hyphenated Words
Hyphenated compounds are where the four major style guides genuinely disagree with each other, not just differ in wording. The core question: when a word like "well-known" appears in a title, does the part after the hyphen get its own capital letter?
| Style Guide | Rule | Example |
|---|---|---|
| AP | Capitalize both elements of a hyphenated compound. | Well-Known, Self-Aware, Twenty-Five |
| Chicago | Capitalize the second element unless it's a suffix that couldn't stand alone as a word, or the first element is a prefix that couldn't stand alone. | Well-Known, but Anti-intellectual and Co-worker |
| APA | Capitalize both elements if either one would be capitalized on its own as a major word. | Well-Known, Twenty-First |
| MLA | Capitalize each element as if it were a separate word in the title. | Well-Known, Self-Aware |
Chicago is the outlier. It only capitalizes the second half of a hyphenated compound if that half could function as an independent major word - which is why Chicago writes "Well-Known" (both "well" and "known" work as standalone words) but lowercases the second half of words like "anti-intellectual" or "co-worker," where "intellectual" and "worker" are the real words and the first half is just a prefix. AP, APA, and MLA don't make that distinction and simply capitalize both halves. For more on how the four guides differ overall, see our AP vs Chicago vs APA vs MLA comparison, and for the other most common capitalization slip-ups, see our 15 common title case mistakes guide.
If you don't know which style guide applies, capitalizing both halves is the safer default - three of the four major guides do it that way, and it looks correct in the vast majority of real-world titles.
Frequently Asked Questions
Do you capitalize numbers in a title?
Numerals like 5, 10, or 2026 don't have a "case" to change, so they stay exactly as written no matter where they fall in the title. Spelled-out numbers like "Five" or "Ten" are different - they're treated as ordinary major words and capitalized just like any noun or adjective would be, regardless of how short they are.
How do you capitalize an ordinal number like 21st in a title?
Leave the letter suffix lowercase. "21st Century" is correct; "21St Century" is not, because the "st" is a suffix attached to the numeral, not a standalone word that gets its own capitalization treatment. The same goes for 1st, 2nd, 3rd, and every other ordinal suffix.
Are acronyms like NASA or FBI capitalized in a title?
Yes, and they keep their full standard capitalization regardless of where they land in the title or how short they are. The rule that shortens articles and prepositions to lowercase (like "a" or "in") doesn't apply to acronyms and initialisms - "FBI" stays "FBI" whether it opens, closes, or sits in the middle of a headline.
Should U.S. have periods in a title?
That depends on which style guide you're following, not on title case itself. AP style traditionally uses "U.S." with periods. Many web and tech style guides drop the periods and use "US." Either way, once you've picked a format, keep both letters capitalized - title case doesn't change an abbreviation's internal capitalization.
Do you capitalize both parts of a hyphenated word in a title?
Usually yes, but Chicago is the exception. AP, APA, and MLA all capitalize both elements of a compound like "Well-Known." Chicago capitalizes the second element only if it would be a major word on its own - so it writes "Well-Known" but lowercases the second half of words like "Anti-intellectual" or "Co-worker," where the second element can't stand alone as an independent word.
How do you capitalize a.m. and p.m. in a title?
Keep them lowercase with periods, even though the rest of the title is in title case - "a.m." and "p.m." are treated as fixed technical abbreviations, not ordinary words subject to the major/minor word rules. If a title would otherwise start with one, it's worth rewording so the sentence doesn't open on it.
Is "vs." capitalized in a title?
No. "Vs." (short for "versus") stays lowercase with its period intact in the middle of a title, similar to how a.m./p.m. are handled - it's a fixed abbreviation rather than a word that follows the usual capitalize-major-words rule. It would only be capitalized if it happened to be the first or last word.
Do decades like the 1990s get an apostrophe or capital S?
No capital letter either way - "1990s" and "'90s" both keep the trailing "s" lowercase, since it's just a plural marker rather than a separate word. If you're dropping the century, use an apostrophe before the two-digit year ("'90s," not "90's," which misplaces the apostrophe).
Try our free title capitalization tool - it handles numbers, abbreviations, and hyphenated words correctly for AP, Chicago, APA, and MLA, so you don't have to memorize any of these tables.