Some confusion arises over the use of the term capital in reference to a seat of government. The word, from the Latin term capitalis, stemming from the root word capit, meaning “head,” applies to the city in which the government of a nation, state, or other political jurisdiction is based. (Loosely, it can also apply to the center of a social or artistic movement.)
However, the word is sometimes confused with capitol, which shares an etymology with capital but comes down to us directly from the name of the Capitoline Hill, one of the fabled seven hills of Rome, where the Capitolium, a temple built in Rome to honor Jupiter, was located. (Such temples, known collectively as capitolia, were common in the Roman Empire.) From that usage is derived the meaning of a building or group of buildings where a legislative body meets or where other governmental functions occur.
This term, as a proper noun, is the name of the building in which the US Congress, consisting of the Senate and the House of Representatives, meets. By extension, it also refers to buildings with similar functions in all the state capitals of the United States, as well as Puerto Rico, and in several other countries in the western hemisphere. (The French city of Toulouse, by comparison, has its Capitole; the original building was constructed in the late 1100s by the capitouls, or city magistrates, and they met in a chamber called the capitulum.)
The correct relationship between the two terms is represented in the sentence “The capitol is located in Washington, DC, the nation’s capital.” (When referring to the building itself, one writes “the Capitol Building.”)
The word capitol has been adopted by several companies (for example, Capitol Records) and in other contexts (the board game Capitol), but its meaning is specific. Capital, however, has several meanings stemming from various senses associated with the meanings “head” or “top.”
It is the name for the uppermost portion of a column (from capitellum, or “small head”), and refers to an uppercase letter. It is associated with crimes punishable by death and with execution itself. As an adjective, it also refers to something that is most important or most serious, or it is employed as a superlative. Capital is also used in financial contexts or figurative extensions, referring to funds or stocks, or meaning “advantage” or “assets,” and it is the root of the term capitalism.
Interestingly, a variant of the term was also a title of nobility in limited usage in medieval France. One of the lords of Buch (one of four localities where the title was used), referred to in historical accounts as the Captal de Buch, was a prominent figure in France’s conflicts with England during the Hundred Years’ War. (In a related note, the root word also figures in the word captain, referring to the head of a military unit.)