Is number four in roman numerals write as IV or IIII please give the reasons

The number four in Roman numerals is written as "IV". Here are the reasons and principles that govern this representation:

1. Value and Alphabetic Symbols:

   • Roman numerals have specific symbols which represent values: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1000.

2. Combining Symbols:

   • Multiples of a value can be combined by placing the symbol next to itself. For example, "II" represents 2, "VV" would represent 10 (if it were used, but it isn't because of the subtractive principle).

3. Subtractive Notation:

   • When a smaller numeral appears before a larger one, the smaller numeral is subtracted from the larger. This is a key rule that leads to "IV" for four rather than "IIII".
   • "IV" is read as "one less than five," which equals 4.

4. Simplification:

   • Roman numerals tend to combine and simplify numbers as much as possible, avoiding unnecessary repetition of symbols. "IIII" would represent four ones, but it doesn't follow the rule of subtractive notation.

5. Consistency:

   • The use of "IV" ensures consistency with other numerals that use the subtractive principle, like "IX" (9) and "XL" (40). Using "IIII" would break this pattern and make the numeral system inconsistent.

6. Historical Usage:

   • Historically, Romans used "IV" for the number four, and this usage has been continued through modern times for consistency and clarity.

In conclusion, while "IIII" may seem like an alternative because it contains four 'I's, the correct and traditional representation of the number four in Roman numerals is "IV" due to the principles of value combination and the subtractive notation.