ra·di·us 
(rādē-əs)
(rādē-əs)n. pl. ra·di·i (-dē-ī′) or ra·di·us·es
1. Abbr. r or rad. Mathematics
a. A line segment that joins the center of a circle with any point on its circumference.
b. A line segment that joins the center of a sphere with any point on its surface.
c. A line segment that joins the center of a regular polygon with any of its vertices.
d. The length of any such line segment.
2. A circular area measured by a given radius: every family within a radius of 25 miles of the city center.
3. A bounded range of effective activity or influence: the operating radius of a helicopter.
4. A radial part or structure, such as a mechanically pivoted arm or the spoke of a wheel.
5. Anatomy
a. A long, prismatic, slightly curved bone in humans, the shorter and thicker of the two forearm bones, located on the lateral side of the ulna.
b. A similar bone in many other vertebrates.
[Latin, ray, spoke of a wheel, radius; see RAY1.]
- Symons
- sympathectomy
- sympathetic
- sympathetically
- sympathetic ink
- sympathetic nervous system
- sympathize
- sympathizer
- sympathizingly
- sympatholytic
- sympathomimetic
- sympathy
- sympathy strike
- sympatric
- sympatrically
- sympatry
- sympetalous
- symphonic
- symphonic poem
- symphonious
- symphoniously
- symphonist
- symphony
- symphony orchestra
- symphyseal