What is "zetta-"

pre. In the International System of Units and other metric systems of units, multiplying the unit to which it is attached by 10²¹. Symbol: Z

Zetta is a decimal unit prefix in the metric system denoting a factor of 10 or . The prefix was added as an SI prefix to the International System of Units (SI) in 1991 and has the symbol Z.

Zetta is evocative of the Latin numeral , meaning "seven". Therefore it was used to denote the seventh power of 1000.

A prefix of the same value, hepta, was informally introduced a few years before the promulgation of zetta. It was formed from the Greek , also meaning "seven". Hepta never received official sanction and is obsolete. Zeta , although being the 6th letter of the Greek alphabet, denotes a value of seven (7) when used as a numeral.

Examples:

• The mass of Earth's atmosphere is approximately 5 zettagrams (Zg).
• The volume of seawater in the Earth's oceans is approximately 1.369 zettalitres (Z).
• Avogadro's constant is 602.2 zettamol (Zmol).
• Estimates of the diameter of the Milky Way Galaxy are between 0.9 and 1.7 zettametres (Zm).
• A zettabyte (ZB) is a quantity of information or information storage capacity equal to 10 bytes, 1000 bytes, 1,000 exabytes or 1 sextillion bytes. The zebibyte (ZiB) is a related unit that uses a binary prefix, and means 1024 bytes.