A terabyte (derived from the SI prefix tera-) is a unit of information or computer storage equal to one trillion (one long scale billion) bytes. It is commonly abbreviated TB.

Because of irregularities in definition and usage of the kilobyte, the exact number of bytes intended may be either of the following:

1. 1,000,000,000,000 bytes - 1000⁴ or 10¹².
2. 1,099,511,627,776 bytes - 1024⁴ or 2⁴⁰. This capacity may be expressed unambiguously as a tebibyte.

gigabyte << terabyte << petabyte

Terabytes in use

A typical video store contains about 8 terabytes of video. The books in the largest library in the world, the U.S. Library of Congress, contain about 20 terabytes of text.

Personal computers containing a terabyte or more of storage space have recently become possible using combinations of high-capacity mass-market hard drives. As of April, 2005, commerical hard drives exceeded 400 gigabytes in size, so storage capacity totalling a terabyte or more can be reached using as few as 2 or 3 hard disks, at a street cost of as little as USD $450, down from over USD $1000 in 2003. (source: www.newegg.com)

LaCie also makes a family of hard drives called "The Bigger Disks" that hold up to two terabytes of data.