Definition from Wiktionary, the free dictionary
From Ancient Greek ἑπτά (heptá), for the seventh order of 103. The consonants pt are reduced to tt as in Italian, by analogy with peta-; the letter z was added, as a start to running through the alphabet backwards.
- In the International System of Units and other metric systems of units, multiplying the unit to which it is attached by 1021. Symbol: Z