Etymology of Units

by PC Hariharan
  1. Kilo Greek khilioi = 1000
  2. Mega Greek megas = great, e.g., Alexandros Megos
  3. Giga Latin gigas = giant
  4. Tera Greek teras = monster
  5. Peta Greek pente = five, fifth prefix, peNta - N = peta
  6. Exa Greek hex = six, sixth prefix, Hexa - H = exa
    Remember, in standard French, the initial H is silent, so they would pronounce Hexa as Exa. It is far easier to call it Exa for everyone's sake, right?
  7. Zetta almost homonymic with Greek Zeta, but last letter of the Latin alphabet
  8. Yotta almost homonymic with Greek iota, but penultimate letter of the Latin alphabet.
The first prefix is number-derived; second, third, and fourth are based on mythology. Fifth and sixth are supposed to be just that: fifth and sixth. But, with the seventh, another fork has been taken. The General Conference of Weights and Measures (CGMP, from the French; they have been headquartered, since 1874, in Sevres on the outskirts of Paris) has now decided to name the prefixes, starting with the seventh, with the letters of the Latin alphabet, but starting from the end. Now, that makes it all clear! Remember, both according to CGMP and SI, the prefixes refer to powers of 10. Mega is 10**6, exactly 1,000,000, kilo is exactly 1000, not 1024.

End of Etymology of Units 101.

You might also like to check out The Peta Principle, by Jim Binder, of the San Diego Supercomputer Center, and read this extract from The Jargon File, which suggests abandoning greek letters and using the names of the Marx Brothers instead.

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