Definition of peri- in US English:

peri-

prefix

  • 1Around; about.

    ‘pericardium’
    ‘peristyle’
    ‘perimeter’
  • 2Astronomy
    Denoting the point nearest to a specified celestial body.

    ‘perihelion’
    Compare with apo-
    ‘perilune’

Origin

From Greek peri ‘about, around’.