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 equivalent of the number 42 is XLII. The Roman numeral system uses letters to denote numbers. The basic Roman numerals used to write numbers up to 100 are as follows: I equals one, V equals five, X equals 10, L equals 50 and C equals 100.