I am from the USA and I have never heard of this tonne being US versus UK. I hardly ever use the term tonne(s), whereas I have used ton on several occasions. Also, the dictionary does not have your description of tonne. Finally, your description does not really agree with my previous post. Will you please cite your source? I believe you have this mixed up with the relationship between long ton and short ton. My understanding is that tonne is a metric measurement not Avoirdupois (U.S.).