Trillion
English usage
In most English-speaking countries (and in English Wikipedia), a trillion is equal to 1 000 000 000 000 or 1012 (a one followed by twelve zeros). It is a thousand billion (English usage) or a million million or one thousandth of a quadrillion (English usage). While the United Kingdom, Ireland, Australia and New Zealand traditionally employed the non-English usage, some years ago they largely switched to the more common English usage of 1012.
Non-English Usage
In many European languages, the word "trillion" or its equivalent is used for 1 000 000 000 000 000 000 or 1018 (a one followed by eighteen zeros). The Greek usage for trillion is equivalent to the English usage.
History
The history of trillion is described in the billion article.
Ambiguity
For reasons of the ambiguity described here, it is preferable to avoid the usage of the term trillion and instead use the corresponding powers of ten or SI prefixes as appropriate. However, many people use the word trillion to mean an
unspecified large number. Then it falls into the same category as umpteen and gazillion.
See also