Definition

1. Noun:
   • A straight line segment from the center to the circumference of a circle or sphere: This is the primary geometric meaning, referring to the line itself.
   • The length of such a line segment: This refers to the measurement or distance.
   • A circular area defined by a given distance from a central point: This extends the geometric concept to describe a region or range.
   • A radiating line or structure: This refers to a part resembling a spoke, such as in a wheel or a body part.
   • A bone in the forearm: In anatomy, it is the shorter of the two bones in the human forearm, on the thumb side.

Usage Examples

• Geometric Line/Length:
  • Draw a circle with a radius of 5 centimeters.
  • The radius of the Earth is approximately 6,371 kilometers.
• Circular Area:
  • The search for the missing hiker focused on a ten-mile radius around the trailhead.
  • Most of our customers live within a small radius of the store.
• Radiating Structure:
  • The bicycle wheel has 36 spokes, each a radius connecting the hub to the rim.
• Anatomy:
  • He fractured his radius in a skiing accident.

Advanced Usage

• "Within a radius of": Used to specify the extent of a circular area from a central point.
  • The explosion damaged buildings within a radius of 500 meters.
• "Radius of action/curvature": Technical terms used in physics, engineering, and military planning.
  • The fighter jet's radius of action limits how far it can fly on a mission.
  • A tighter radius of curvature makes a road more dangerous at high speeds.

Variants and Related Words

• Radii (n): The standard plural form of "radius."
  • The data points are located at different radii from the center.
• Radial (adj): Relating to, arranged like, or moving along a radius or ray.
  • The city has a radial street pattern extending from the central square.
• Radial (n): A radial tire or a radial part.

Synonyms

• Semidiameter: (Technical) Half the diameter; synonymous with the length meaning of radius.
• Range: Similar to the "circular area" meaning, indicating a sphere of action or influence.
• Reach: Similar to "range," indicating the distance something can cover.
• Spoke: Similar to the "radiating structure" meaning in the context of a wheel.

Related Phrases

• Radius vector: (Mathematics/Physics) A line from a fixed origin to a point, especially in polar coordinates.
• Atomic radius: (Chemistry) A measure of the size of an atom.
• Turning radius: (Engineering) The minimum space needed for a vehicle to make a circular turn.

Noun

1. support consisting of a radial member of a wheel joining the hub to the rim
2. the outer and slightly shorter of the two bones of the human forearm
3. a circular region whose area is indicated by the length of its radius
   • they located it within a radius of 2 miles
4. a straight line from the center to the perimeter of a circle (or from the center to the surface of a sphere)
5. the length of a line segment between the center and circumference of a circle or sphere