Tonne
Pronunciation
Usage notes
A tonne (about 2204.6 pounds) is not exactly the same as a long ton (2240 pounds). Because "ton" and "tonne" usually have the same pronounciation, the phrase "metric ton" is frequently used for "tonne" where disambiguation is required.
In the 1970s the British steel industry promoted the pronounciation /ˈtʌnɪ/ to help avoid confusion. The pronounciation /tɒn/ has also been used for the same reason.
1971. Transactions of the Royal Institute of Naval Archtects, page 215, volume 113, 1971
The metric ton or 'tonne' is accepted as a synonym for the megagramme, and this form Is to be preferred on the grounds of brevity and familiarity in the industry. It may be as well to use the pronunciation 'tunnie' until the risk of confusion with the old ton has passed.
1972, Which, May 1972
The British Steel Corporation, going metric but realising the possible confusion between a ton and a tonne (1,000 kilograms) has directed its staff to pronounce ‘tonne’ ‘tunnie’.
2002, Richard Chapman, Physics for Geologists, page 138, CRC Press, 2002 ISBN 0415288053
The tonne rhymes with con (perhaps not in North America!) to distinguish it from the non-SI unit of weight, the ton rhyming with bun.