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.
The Roman numeral XLV translates into the number 45.. The Roman numeral system uses letters to represent numerals in a number. Letters used for numbers up through 100 are 'I for one, V for five, X for 10, L for 50 and C for 100.