Byte

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Look up peta- in Wiktionary, the free dictionary.

Peta- (symbol: P) is a prefix in the metric system denoting 10¹⁵ or 1000000000000000. For example:

1 petametre = 10¹⁵ metres
1 petasecond = 10¹⁵ seconds
1 petabyte = 10¹⁵ bytes

Adopted in 1975, it was derived from the Greek πέντε, meaning "five", because of the five in 1000⁵, for which it stands. The peta- prefix is similar to the penta- prefix (for "five"), but without the letter n. This omission is modelled on the way the similar tera- prefix (actually from Greek τέρας = 'monster') for 1000⁴ seems to omit a letter from the tetra- prefix (for "four").

Examples:

• the mass–energy equivalence is 89.9 PJ/kg
• 1 light-year = 9.461 Pm

In computer science peta- can sometimes mean 1125899906842624 (1024⁵ or 2⁵⁰), instead of 1000000000000000, especially when used to prefix the byte, giving a petabyte. To resolve this ambiguity, the term pebibyte has been suggested to mean 2⁵⁰ bytes.

See also

• Binary prefix

Notes and references

External links

• BIPM website