“capital” vs. “capitol”
Write "capitol" only when naming an actual legislative building with a dome; for a nation's or state's seat of government as a city, for money and assets, for uppercase letters, or for the adjective meaning excellent or punishable by death, write "capital."
capital
"Capital" covers a cluster of related senses: the city that serves as a seat of government ("Madrid is the capital of Spain"), money or assets used to start or grow a business ("raise capital for the new factory"), an uppercase letter, and an adjective meaning excellent or, in the older legal sense, punishable by death ("a capital offense"). All of these trace to Latin "capitalis," built on "caput" (head), the same root behind "captain" (head of a group) and the now-archaic use of "head" to count cattle — a government capital is the "head city" of a nation, and capital letters historically sat at the "head" of a word or sentence.
capitol
"Capitol," by contrast, names one specific kind of thing only: a building where a legislature meets, most famously the U.S. Capitol in Washington, D.C., and the fifty state capitol buildings that house state legislatures. The word comes from "Capitolium," the Roman name for the Temple of Jupiter on Rome's Capitoline Hill, one of the city's seven ancient hills and the site of its most sacred civic and religious buildings. When the framers of the young United States were naming the new legislative building in Washington, they deliberately borrowed this Roman name to evoke the authority and permanence of republican Rome.
The real distinction
Despite sounding identical, "capital" and "capitol" trace to two different Latin words that only converged in English spelling by historical coincidence: "capital" comes from "caput" (head), while "capitol" comes from "Capitolium," a Roman place name with no etymological link to "head" at all. The most reliable test is architectural: if you're talking about an actual physical building with a dome where lawmakers meet, you need "capitol"; for every other sense — the city, the money, the letter, the adjective — you need "capital." A city is always its country's or state's "capital," never its "capitol," even though that capital city usually contains a capitol building. Confusingly, Washington, D.C. is the nation's capital (the city), and inside it sits the U.S. Capitol (the building) — both words appear correctly in the same sentence describing different things, which is precisely the sentence pattern that trips up writers who assume the words are interchangeable. Journalists covering state governments run into this constantly, since news copy routinely needs both words in close proximity ("lawmakers gathered at the state capitol to debate the capital's growing budget"), and a wrong swap in either direction changes a building into a city or a city into a building. The financial sense of "capital" (money, assets, capital gains, venture capital) has no capitol equivalent whatsoever, which makes any business or finance writing an easy, low-risk zone: if money is involved, it's always "capital."
Examples with “capital”
- Austin is the capital of Texas.
- The startup needed more capital before it could expand.
- Begin every sentence with a capital letter.
- Treason was once considered a capital crime.
- The company relocated its headquarters to the capital city.
- Investors provided the capital needed for the merger.
- Rome has served as Italy's capital since 1871.
- She used capital letters for the entire heading by mistake.
Examples with “capitol”
- Protesters gathered on the steps of the state capitol.
- The U.S. Capitol dome was completed during the Civil War.
- Tour buses stop outside the capitol every morning.
- The governor's office is not inside the capitol building itself.
- Lawmakers debated the bill late into the night at the capitol.
- The capitol was evacuated briefly during the storm warning.
- A statue stands atop the capitol's rotunda.
- Visitors can tour the capitol's historic chambers on weekdays.
Memory trick
Picture the round dome of the Capitol building echoed in the round letter o sitting inside "capitol" — a building with a dome gets the o-spelling. Every other use of the word, from cities to cash to capital letters, keeps the more common a-spelling of "capital." If you can replace the word with "the dome-building where the legislature meets" and the sentence still works, you need "capitol"; if you can replace it with "the seat of government," "funds," or "uppercase," you need "capital."