radii

noun

1. (form-of, plural)plural of radius

   “The radius of the Sun is equal to about 109 Earth radii.”

   “Now the centrifugal forces of bodies revolving in the ſame time in different circles being to one another as the radii of the circles (as ſhall be ſhewn when I come to treat of thoſe forces) it follows that the centrifugal force muſt be greateſt at the æquator, and thence be continually diminished towards the poles.”