Yours, Etc.: Origins and Uses of 8 Sign-Offs
acronym for People for the Ethical Treatment of Animals; the group’s website says it was founded in 1980.
peta- pref. One quadrillion (1015): petagram.
A prefix that means:
One quadrillion (1015), as in petahertz, one quadrillion hertz.
250 (that is, 1,125,899,906,842,624), which is the power of two closest to a quadrillion, as in petabyte.