the number four in roman numerals sometimes can also be written as IIII instead of IV

In Roman numerals, the number four is correctly written as "IV." The use of "IIII" to represent the number four is not standard and is often considered an error. Here's the breakdown:

• I represents 1.
• V represents 5.
• X represents 10.

The principle of subtractive notation in Roman numerals allows using a smaller numeral before a larger one to mean subtraction. For example, "IV" means "5 - 1" which equals 4. The use of "IIII" to represent four would be like saying "1 + 1 + 1 + 1," which does not follow the subtractive notation rule.

So, the correct representation for the number four is "IV," and you should use this form when writing Roman numerals.