PCO stands for Potential Change Order (construction management). Suggest new definition. This definition appears somewhat frequently and is found in the following Acronym Finder categories: 1  Business, finance, etc.
Quick Answer. The Roman numeral XIX is the number 19. X is the number 10, and I is the number one. When a lower number is placed in front of a larger number, it indicates subtraction; IX is the same as 10 minus one, which equals nine. The Ancient Romans used different letters to represent numbers.
Today we write out 99 in Roman numerals as XCIX because XC = 90 and IX = 9. Therefore it logically follows that XC+IX = XCIX as in the case of Hindu-Arabic numerals. But the R â¦ oman numeral system does not contain a zero figure for positional place value purposes.   The seven symbols used for Roman numerals are:-   M=1000, D=500, C=100, L=50, X=10, V=5 and I=1    Roman numerals are the numbering system that the Romans used.