# Definition of radius in English:

### Pronunciation /ˈrādēəs//ˈreɪdiəs/

• 1A straight line from the center to the circumference of a circle or sphere.

‘Thus, the area of a circle is equal to half of the product of the radius and the circumference.’
• ‘He calculates the side of a regular pentagon in terms of the radius of the circumscribed circle.’
• ‘Recall that given a circle of radius r, the circumference is 2pr.’
• ‘Note that this curvature is the inverse of the radius of a circle tangent to the neutral line at this point.’
• ‘David Gregory used p/r for the ratio of the circumference of a circle to its radius.’
• ‘The hexagon is a function between the radius and circumference of the circle, and is a naturally occurring form in nature.’
• ‘A circle and square have an equal area only if the ratio between a side of the square and a radius of the circle equals the square root of pi.’
• ‘It states that the centre of gravity of a semicircle divides the radius in the ratio 3: 7.’
• ‘A circle of radius 6 is circumscribed by a square of side-length 12.’
• ‘Given an angle CAB draw a circle with centre A so that AC and AB are radii of the circle.’
• ‘The particular tablet which interests us here investigates how to calculate the radius of a circle through the vertices of an isosceles triangle.’
• ‘And, if anything, I'm quite nearly positive that Lancome is the guy who discovered the constant ratio of a circle's radius to its circumference.’
• ‘Because the slices are thin, the height of the rectangle is approximately the radius, r, of the circle.’
• ‘Company officials like to say that Rhino can go beyond high-school geometry, beyond straight lines and radiuses.’
• ‘The radii of the given circles and n must stand in a certain relationship for the chain to close on itself.’
• ‘So the radius of the sphere will be 1 and its surface area will be 4 Pi.’
• ‘In the introduction he pointed out that a plane was a special case of a spherical surface, that is a sphere with infinite radius.’
• ‘The point P is on the circumference of the circle of radius b.’
• ‘Users can measure the distance of vertices/edges/faces, the angle of edges/faces, and the radii and diameters of circles.’
• ‘The inverse of the radius of the circle equals the curvature in radians/m.’
1. 1.1A radial line from the focus to any point of a curve.
‘These apply to clear zones on the outside of horizontal curves with a radius of 900 m or less.’
• ‘Key factors to meet the new criteria include the length and width of runways, the width and curve radii of taxiways, and also the airport's pavement loading limits.’
• ‘Second, this lightweight insert extends the bullet nose and accommodates use of a longer ogive - the radius of the curve of the bullet tip.’
• ‘The curve radii and crossfall of the road are measured and fed through algorithms from the Austroads Rural Road Design guide to generate a suggested advisory speed for all points along the road.’
• ‘The upper three curves are the pore radii for the three systems, whereas the lower three are the corresponding standard deviations of the upper curves.’
• ‘A minimum curve radius of 5 feet is suggested for 1/2-inch-diameter strand.’
• ‘Because of the very mountainous terrain and the need for very shallow radius curves, most of the route will be in tunnels, with consequent heavy civil engineering costs.’
• ‘The front rolled edge and curved radius of this striking two-tiered kitchen island can only be accomplished in solid surface material such as granite or Corian (tm).’
2. 1.2The length of the radius of a circle or sphere.
‘The cone shaped tip is just under one micrometer in length and has a radius of a few nanometers at its apex.’
• ‘Interestingly, though the analysis points to a ball with an average radius of 1.584 inches, the measured radius of a real baseball is 1.452 inches.’
• ‘Stephenson, who constructed both projects, believed that gradients should be less than 1 percent and that curves should have very wide radii of at least a kilometre.’
• ‘As skaters pull their arms in, their radius decreases and they spin faster.’
3. 1.3A specified distance from a center in all directions.
‘there are plenty of local pubs within a two-mile radius’
• ‘It seems sensible to find somewhere with no population centres within a two-mile radius - like offshore.’
• ‘The department has acquired legal powers to close all footpaths within a two-mile radius of any free-range poultry farms.’
• ‘Teams divided into four groups, combing through a two-mile radius searching for any clue of what might have happened.’
• ‘The Ride Safe program provides rides for students, staff and faculty members from the Student Life Centre to their homes within a certain radius around campus.’
• ‘A check of directories shows 37 hotels and motels within a three-mile radius of Florence and LaSalle.’
• ‘Tests results Tuesday showed that all 20 farms within a two mile radius of the original infected farm were negative for avian influenza.’
• ‘We do not allow students who live within a five-mile radius to use their cars to come to college.’
• ‘Those deemed more at risk of exposure are those who lived within a one-kilometer radius of the factory for more than 20 years between 1962 and 1987.’
• ‘Police are investigating links between the arson attack on December 27 and another three within a half-mile radius over the last few days.’
• ‘He concluded: ‘This year, I will enter half a dozen local races, all within a radius of 50 miles, and hope to do pretty well.’’
• ‘It should be known in this connection that according to the relevant law, no structure of any kind can be built within a radius of 100 metres of any registered national monument.’
• ‘But one recommendation to come out of it was that masts should not be located within a radius of 500 metres of schools and homes.’
• ‘B & Bs within a three-mile radius of the town were full.’
• ‘The IT professionals usually look out for areas surrounding a radius of 9 km from City Railway Station.’
• ‘To calculate a radius for each hospital's market area, we limited radii to a range between 10 and 35 miles.’
• ‘The explosions could reach a radius of 25 meters.’
• ‘I spent half a century here, most of it within the confines of a small radius.’
• ‘Day said location is key when making an investment and believes investors should focus on the coastal strip within a 10-mile radius of the city.’
• ‘Once Keaton laughed so hard he scared all the birds within a ten-foot radius out of their perches.’
• ‘At half-mile intervals, they stop and count the birds they see or hear within a radius of a quarter mile.’
• 2Anatomy
The thicker and shorter of the two bones in the human forearm.

‘Common osteoporotic fracture sites include the vertebrae, the hip, the distal radius of the forearm, and the proximal humerus.’
Compare with ulna
• ‘Scaphoid fractures are rare children and the elderly because of the relative weakness of the distal radius compared with the scaphoid in these age groups.’
• ‘Abduction is movement of the hand away from the body as the proximal carpal bones move medially on the radius.’
• ‘He also had tenderness bilaterally over the distal radius and ulna, and anterior tibia.’
• ‘Bone mineral density was measured at the lumbar spine, radius, hip and femoral neck.’
1. 2.1Zoology The corresponding bone in a vertebrate's foreleg or a bird's wing.
‘For example, the radius, one of the lower bones of the foreleg, became much broader.’
• ‘As is usual in chelonioids, the radius is notably longer than the ulna.’
• ‘In the equid foreleg, radius and ulna are united, and the ulna is greatly reduced so that all weight is born on the radius.’
• ‘The humerus, radius, and ulna of Adriosaurus appear to be slightly wider than those of the current specimen, but this is probably a result of crushing.’
• ‘To fit a horse radius into a human forearm would require a physique to rival Popeye.’
2. 2.2Entomology Any of the main veins in an insect's wing.
• 3Zoology
(in an echinoderm or coelenterate) any of the primary axes of radial symmetry.