This chapter discusses Roman numerals and their application in the apothecary system. It covers how to convert between Roman numerals and Arabic numbers, and how Roman numerals were historically used in timepieces and to denote drug quantities like aspirin grains. Safety issues around abbreviations are also mentioned. Roman numerals use letters like I, V and X to represent values, while Arabic numbers use 1, 2, 3. Rules are provided for adding or subtracting Roman numerals based on their position and relative values.

1. Gray Morris Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.

2. Unit One: Chapter 1 Mosby items and derived items © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.