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noun [countable]

a unit of computer measurement equal to 1,000,000,000,000 bytes

'If there's a storage fanatic in your family, a perfect gift could be coming for her or him toward the end of the year: 1 terabyte hard drives. Desktop hard drives holding 1 terabyte, or 1,000 gigabytes, of storage will likely debut in 2006 …'

USA Today 15th August 2006

'We're all familiar with terms like kilobyte, megabyte, and even gigabyte, but what about terabyte? If mega- and gigabytes are beginning to seem like small beer relative to your computer storage needs, then worry not – it looks as if the age of the terabyte, a storage capacity equivalent to about 1,000 gigabytes, is just around the corner.

Although it's unlikely the average home computer user would need as much as a terabyte of storage, the rising popularity of other technical devices is pushing the development of larger capacities

Commonly abbreviated to TB, a terabyte is approximately one trillion bytes, or in precise terms: 1,099,511,627,776 (this exact figure is sometimes alternatively referred to as a tebibyte). In the summer of 2006, electronics company Hitachi announced its intention to release one-terabyte hard drives by the end of the year.

Although it's unlikely that the average home computer user would need as much as a terabyte of storage, the rising popularity of other technical devices is pushing forward the development of larger capacities. A key area is cars, with memory-hungry in-car entertainment systems, and sophisticated GPS (Global Positioning Satellite) navigation devices. High-definition (HD) video is another area, with the increased use of digital video recorder hard drives, and TVs which include these as an integrated component. Half a terabyte (=500 gigabytes) would be enough capacity for storage of around 80 hours of HD video recordings. If music's your thing, one terabyte has the capacity to store more than 240,000 songs!

Background – terabyte

Tera- in the word terabyte is a combining form used in units of measurement to represent a factor of 1012, also occurring, for example, in the electrical measurements terawatt and teravolt. It actually derives from the Greek form teras, meaning 'monster'.

Though a terabyte might seem like a massive amount of computer storage, it is in fact not the highest unit so far conceived. This record goes to the yottabyte (commonly abbreviated to YB), which is the equivalent of 1024 zettabytes (ZB), which itself represents around 1000 exabytes (EB), which (surprise surprise) is about 1000 petabytes (PB). A petabyte is, you've guessed it, approximately 1000 terabytes.

In 2003, a report from the University of California, Berkeley, claimed that five exabytes of data had been estimated to be equal to 'all words ever spoken by human beings'. Though interesting in theory, the validity of the estimate has been disputed.

by Kerry Maxwell, author of Brave New Words

This article was first published on 25th September 2006.

Open Dictionary

Dunning-Kruger effect

the phenomenon by which an incompetent person is too incompetent to understand his own incompetence

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