What is an avoirdupois ounce?
An avoirdupois ounce is the ordinary ounce of the imperial and US customary systems, as opposed to the troy ounce used for gold and silver.
It is equal to 1/16 of a pound or approximately 28.35 grams. The avoirdupois system is based on a pound of 16 ounces, with larger units such as tons and pounds used for heavier measurements.
What are Troy Pounds?
A troy pound is about 373.24 grams, which makes it lighter than the avoirdupois pound of 453.59 grams. It was the pound of the precious metals trade, though gold and silver are now quoted per troy ounce.
One troy pound is equivalent to 12 troy ounces, which is lighter than the avoirdupois pound commonly used in everyday measurements. The troy pound is often denoted by the symbol "lb t" to distinguish it from the avoirdupois pound.