peta-

In units of measurement, a factor of 10¹⁵.

Adapted from penta‑, five, on the pattern of other SI (Système International) multiples (see the entry Words for multiples).

The prefix appears most often in measures of computer data, such as petabyte; outside this field it is rare, though petagram (a multiple of a thousand million metric tonnes) sometimes appears in discussions of the global carbon cycle.