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.
Roman Numerals are what Romans used to use for numbers. Different symbols have different numeral values. For example, I = 1, V = 5, and X = 10. When these symbols are combined â¦ in different ways the other numbers are formed.   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.