What number is there no Roman numeral for?

Answer 1

The is no Roman Numeral for:

1. Zero

2. Any decimal (0.5) or fraction (1/2) Note: The Romans had a separate system for fractions based on 12 (like a clock). The fractions were made up from dots and the letter S. S =1/2 and each dot was 1/12. Dots alone represented 1/12 (.) to 5/12 (::.) , S was 6/12, S and dots represented 7/12 (S.) to 11/12 (S::.) and I was one.

3. Any imaginary number (i)

4. Numbers past the low Millions (M with a bar over it was Million, the symbol was repeated to represent multiple millions)