do number four in roman numerals must be always written as IIII instead of IV under any conditions

No, the number four in Roman numerals should always be written as "IV" rather than "IIII." The use of "IIII" is actually considered incorrect and not the standard representation of the number four in Roman numerals. Here's why: 1. **Subtractive Principle:** The Roman numeral system uses a subtractive principle for certain values. In the case of "IV," the "V" (five) has one "I" (one) subtracted from it to represent the value of four. 2. **Standard Notation:** The form "IV" is the universally accepted way to write the number four in Roman numerals. Using "IIII" would be non-standard and could lead to confusion. 3. **Historical Standardization:** Over time, as the Roman numeral system became more standardized, the subtractive notation became the norm. 4. **Clear Representation:** "IV" clearly communicates the value of four using the established rules of Roman numerals. 5. **Avoidance of Ambiguity:** Using "IIII" could potentially be mistaken for the number one when read quickly or in certain contexts. While you might occasionally see "IIII" used in less formal contexts or as a decorative element (such as on some older clocks), it is not the correct representation of the number four in Roman numerals. The correct and universally accepted form is "IV."