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gig·a·byte (gĭgə-bīt, jĭg-)
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n.
1. A unit of computer memory or data storage capacity equal to 1,024 megabytes (230 bytes).
2. One billion bytes.

Usage Note: The usual meaning of the prefix giga- is one billion, so one would expect the term gigabyte to refer to one billion bytes. However, in describing the capacity of an electronic device that stores digital data, it often has a special meaning, referring to the power of 2 closest to one billion, which is 230, or 1,073,741,824 bytes. This special meaning comes about because storage devices use binary numbers to keep track of storage locations, and so are often designed with a number of storage locations that is a power of 2. Nonetheless, for reasons of convenience manufacturers of hard drives generally use gigabyte when they mean a rounded off sum of 1 billion bytes. In other aspects of technology, such as data transmission, where powers of 2 are less relevant, a gigabyte normally means exactly 1 billion bytes. Other prefixes, such as mega- and tera-, show a similar pattern in use.

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
 

Indo-European & Semitic Roots Appendices

    Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:

    Indo-European Roots

    Semitic Roots

    The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.

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