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 is an old decimal numeric system which represents the numbers as combinations of the following Latin letters: I, V, X, L, C, D, M (Roman Numerals Symbols). By using combinations of these symbols it is possible to record Roman Numeral Numbers. This system based on 7 Roman Numeral Symbols was invented and used by the Romans starting from the 7th - the 6th century BC and almost till the late Middle Ages.