A supercarrier is a word sometimes used to describe a form of aircraft carrier with no official meaning. It is generally considered to be 75,000 tons or greater in displacement — most countries operate carriers with displacement less than 40,000 tons (such as Charles de Gaulle), and more often closer to 15,000 (such as HMS Illustrious).
The 81,000-ton USS Forrestal was the first operational supercarrier, though USS United States would have been if she had not been cancelled. The word was first used by the New York Times in 1938 to describe HMS Ark Royal (at a meager 22,000 tons). Most modern supercarriers are of the US Nimitz class at around 100,000 tons, nuclear-powered with crews of over 5,000.
US Supercarriers
The United States Navy operates the world's largest fleet of supercarriers. The Nimitz class, first commissioned in 1975, consists of ten nuclear-powered carriers. These vessels carry approximately 90 aircraft and can operate for over 20 years without refueling.
Other Nations
France operates the nuclear-powered Charles de Gaulle at 42,000 tons. The United Kingdom's Queen Elizabeth class carriers displace 65,000 tons. China commissioned the Liaoning (ex-Varyag) and has built additional carriers domestically.