Apothecary System Ruless

#1

The abbreviation or symbol for a unit of measure is written before the amount or quantity in lowercase letters. (Example: six grains = gr 6 or gr vi).

#2

Roman numerals, as well as Arabic numbers, are used. When Roman numerals are used, they are written in lowercase letters. To prevent errors in interpretation, a line is sometimes drawn over lowercase Roman numerals. A lowercase “i” is dotted above the line. (Example: gr v).

#3

Fractions are used to express quantities that are less than one. (Example: gr 3/4)

#4

The symbol “ss” is used for the fraction 1/2 and it can be written as ss or ss with a line above

#5

A combination of Arabic numbers and fractions can also be used to express units of measure. (Example: gr 7 ½)