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.
There is more than one type of ton
There are three common types of ton; the metric ton (tonne), long ton and short ton.
The metric tonne, also spelled metric ton, is 1,000 kilograms or about 2,204.62 pounds, and it is the one used in countries that have gone metric. More on this unit here: Metric Tonne.
The Long Ton, also known as the Imperial Ton, is the ton of the United Kingdom and is equivalent to 2,240 pounds or about 1,016 kilograms. Further information can be found here: Long ton (Imperial ton).
The short ton is used predominantly in the United States and is equivalent to 2,000 pounds. This unit of measurement is commonly used in industries such as shipping, construction, and agriculture. More information here: Short ton (American ton)