This is one of the gotchas that make American and English two different languages with enough similarity that speakers of each can understand speakers of the other most of the time. As noted, a US ton is 2,000 lb while an imperial ton is 2,240 lb (14lb / stone; 2 stone / qtr; 4 qtr / cwt; 20 cwt / ton). US and imperial gallons also differ (1 imp gallon = 1.2 US gallons) and by extension, their pints are also smaller than ours! While we drive on the carriageway and walk on the pavement, they drive on the pavement and walk on the sidewalk. They call cars, automobiles; the wings of those cars they call fenders; what they call "hoods" we call bonnets. Boots are trunks, etc. etc.
While these differences might seem trivial, 'gotchas' await even where the same definition might at first sight seem to apply. Take "proprietary" as an example: Webster's defines this as, "of, relating to, or characteristic of an owner or title holder" and a UK definition is, "goods made up and sent out by the company whose name is on the product". Back in the 1990s, a company I worked for entered into a contract where certain items were to be of "proprietary supply" and each party 'understood' that to mean the other would provide those items. This only came to light when my company had manufactured most of the equipment and were still waiting for the customer to supply the proprietary items. Cost to my company was about US$1.4 million and a lot of good will... (thankfully, I wasn't involved in drafting that contract!)
