ETYM Latin, a staff, rod, spoke of a wheel, radius, ray. Related to Ray a divergent line.
1. A circular region whose area is indicated by the length of its radius.
2. A straight line from the center to the perimeter of a circle (or from the center to the surface of a sphere).
3. The length of a line segment between the center and circumference of a circle or sphere; SYN. r.

The outer and slightly shorter of the two bones of the human forearm.
In biology, one of the two bones in the lower forearm of tetrapod (four-limbed) vertebrates.

A straight line from the center of a circle to its circumference, or from the center to the surface of a sphere.

Stands for Remote Authentication Dial-In User Service,
a security protocol used for centralized authentication,
authorization, and accounting of network access.
Acronym for Remote Authentication Dial-In User Service protocol. A proposed Internet protocol in which an authentication server provides authorization and authentication information to a network server to which a user is attempting to link.