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 Numeral Calculation; 0: not defined : 1: I: 1: 2: II: 1+1: 3: III: 1+1+1: 4: IV: 5-1: 5: V: 5: 6: VI: 5+1: 7: VII: 5+1+1: 8: VIII: 5+1+1+1: 9: IX: 10-1: 10: X: 10: 11: XI: 10+1: 12: XII: 10+1+1: 13: XIII: 10+1+1+1: 14: XIV: 10-1+5: 15: XV: 10+5: 16: XVI: 10+5+1: 17: XVII: 10+5+1+1: 18: XVIII: 10+5+1+1+1: 19: XIX: 10-1+10: 20: XX: 10+10: 21: XXI: 10+10+1: 22: XXII: 10+10+1+1: 23: XXIII: 10+10+1+1+1: 24: XXIV: 10+10-1+5: 25: XXV: 10+10+5: 26: XXVI: 10+10+5+1: 27: XXVII: 10+10+5+1+1: 28 ...