the difference between IV and IIII in roman numerals

In Roman numerals, "IV" and "IIII" both represent the number 4. However, there is a standard notation convention that applies to Roman numerals:

1. IV: This is the correct notation for the number 4 in Roman numerals. The 'I' represents 1, and the 'V' represents 5. According to the subtractive notation used in Roman numerals, when a smaller numeral appears before a larger one (like IV), it's subtracted from the larger numeral. So 'IV' means 5 - 1 = 4.

2. IIII: This notation is technically incorrect because Roman numerals are designed to combine symbols in a logical way to represent numbers. The 'IIII' would represent four ones, but this would be redundant and against the rules of Roman numeral notation which prefer to use distinct symbols like 'V' for 5 and avoid repeated symbols for simplicity and readability.

The Romans themselves did not use 'IIII' for 4, and modern use of Roman numerals also follows this rule. Therefore, you should always use 'IV' for the number 4 when using Roman numerals.