Tera (T) is a prefix used with the metric system that stands for 1,000,000,000,000 (trillion). A unit with the prefix tera is 10 to the 12th power, or one trillion. It is often used in terms of measurement. A good example of where this prefix is used with computers is with a TB (terabyte).

Tera (1 trillion) comes from the Greek word teras or teratos, meaning "marvel, monster," and has been in use since approximately 1947.

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