Roget's 21st Century Thesaurus, Third Edition Copyright © 2013 by the Philip Lief Group.

EXAMPLES FROM THE WEB FOR RADII

The edges of the radii are also smooth, as is the edge of the basal cup.

Parietes and basis permeated by pores; radii not permeated by pores.

When the radii are not developed, the sutures are very often obscure.

Not only Massinger, but many of our old writers, use parallels for radii.

In some of the plans the cells are on a circumference, and in some on radii.

SuccinctlyThe surfaces of spheres are as the squares of their radii.

Equal circles are those the diameters of which are equal, or the radii of which are equal.

Not that in all circles the radii are equal, but only that they are so in the circle ABC.

He is the central figure; all others are but radii emanating from him.

There is no point which serves as a centre to the radii of the administration.

WORD ORIGIN

1590s, "cross-shaft," from Latin radius "staff, stake, rod; spoke of a wheel; ray of light, beam of light; radius of a circle," of unknown origin. Perhaps related to radix "root," but Tucker suggests connection to Sanskrit vardhate "rises, makes grow," via root *neredh- "rise, out, extend forth;" or else Greek ardis "sharp point."

The geometric sense first recorded 1610s. Plural is radii. Meaning "circular area of defined distance around some place" is attested from 1953. Meaning "shorter bone of the forearm" is from 1610s in English (the Latin word had been used thus by the Romans).

Roget's 21st Century Thesaurus, Third Edition Copyright © 2013 by the Philip Lief Group.