The Roman numeral "CDLXXVIII" represents the number 478. In this numeral, "CD" stands for 400, "LXX" represents 70, and "VIII" signifies 8. Roman numerals are a numeral system originating from ancient Rome, using combinations of letters from the Latin alphabet. This system is still used today in various contexts, such as clock faces, book chapters, and movie titles. Understanding Roman numerals can be helpful in interpreting historical documents and artifacts, as well as in recognizing their influence on modern numbering systems.