capitalcapitalcapitalsnoun1the most important city in a country, where the government is: Tokyo is the capital of Japan.2(no plural) (business) a large amount of money that you use to start a business, etc.: When she had enough capital, she bought a shop.3(alsocapital letter) a big letter of the alphabet, used at the beginning of sentences: Please fill in the form in capitals. Names of people and places begin with a capital letter.