The Roman numeral "CCCXLIII" represents the number 343. In this numeral, "CCC" stands for 300, "XL" represents 40, and "III" signifies 3. When combined, these values add up to 343. Roman numerals are a numeral system originating from ancient Rome. They use combinations of letters from the Latin alphabet, specifically I, V, X, L, C, D, and M. This system was widely used throughout the Roman Empire and is still seen today in various contexts, such as clock faces and book chapters.