
Troy
Precise Measurement
 The troy system is used for accuracy in measuring precious items. 
The jeweler measured the diamonds in troy carats.
 Specific Usage
 Troy is not used for everyday items like groceries or postage. 
He knew not to use troy weight for measuring flour.
 Not for People
 The troy system applies to objects, not quantifying people or animals. 
You wouldn't say, 'She weighs 120 troy ounces.'