Adjacent Words

Radius definitions

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Webster's 1828 Dictionary

RA'DIUS, n. [L. id, a ray, a rod, a beam, a spoke, that is, a shoot; radio, to shine, that is, to dart beams. See Ray.]
1. In geometry, a right line drawn or extending from the center of a circle to the periphery, and hence the semidiameter of the circle. In trigonometry, the radius is the whole sine, or sine of 90 degrees.
2. In anatomy, the exterior bone of the fore arm, descending along with the ulna from the elbow to the wrist.
3. In botany, a ray; the outer part or circumference of a compound radiate flower, or radiated discous flower.

WordNet (r) 3.0 (2005)

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

Merriam Webster's

noun (plural radii; also radiuses) Etymology: Latin, ray, radius Date: circa 1611 1. a line segment extending from the center of a circle or sphere to the circumference or bounding surface 2. a. the bone on the thumb side of the human forearm; also a corresponding part of vertebrates above fishes b. the third and usually largest vein of an insect's wing 3. a. the length of a radius <a truck with a short turning radius> b. the circular area defined by a stated radius c. a bounded or circumscribed area 4. a radial part 5. the distance from a center line or point to an axis of rotation

Oxford Reference Dictionary

n. & v. --n. (pl. radii or radiuses) 1 Math. a a straight line from the centre to the circumference of a circle or sphere. b a radial line from the focus to any point of a curve. c the length of the radius of a circle etc. 2 a usu. specified distance from a centre in all directions (within a radius of 20 miles; has a large radius of action). 3 a the thicker and shorter of the two bones in the human forearm (cf. ULNA). b the corresponding bone in a vertebrate's foreleg or a bird's wing. 4 any of the five arm-like structures of a starfish. 5 a any of a set of lines diverging from a point like the radii of a circle. b an object of this kind, e.g. a spoke. 6 a the outer rim of a composite flower-head, e.g. a daisy. b a radiating branch of an umbel. --v.tr. give a rounded form to (an edge etc.). Phrases and idioms: radius vector Math. a variable line drawn from a fixed point to an orbit or other curve, or to any point as an indication of the latter's position. Etymology: L, = staff, spoke, ray

Webster's 1913 Dictionary

Radius Ra"di*us, n.; pl. L. Radii; E. Radiuses. [L., a staff, rod, spoke of a wheel, radius, ray. See Ray a divergent line.] 1. (Geom.) A right line drawn or extending from the center of a circle to the periphery; the semidiameter of a circle or sphere. 2. (Anat.) The preaxial bone of the forearm, or brachium, corresponding to the tibia of the hind limb. See Illust. of Artiodactyla. Note: The radius is on the same side of the limb as the thumb, or pollex, and in man it so articulated that its lower end is capable of partial rotation about the ulna. 3. (Bot.) A ray, or outer floret, of the capitulum of such plants as the sunflower and the daisy. See Ray, 2. 4. pl. (Zo["o]l.) (a) The barbs of a perfect feather. (b) Radiating organs, or color-markings, of the radiates. 5. The movable limb of a sextant or other angular instrument. --Knight. Radius bar (Math.), a bar pivoted at one end, about which it swings, and having its other end attached to a piece which it causes to move in a circular arc. Radius of curvature. See under Curvature.

Collin's Cobuild Dictionary

(radii) 1. The radius around a particular point is the distance from it in any direction. Nigel has searched for work in a ten-mile radius around his home. N-SING: with supp 2. The radius of a circle is the distance from its centre to its outside edge. He indicated a semicircle with a radius of about thirty miles. N-COUNT

Moby Thesaurus

O, air line, ambit, amplitude, annular muscle, annulus, approach, area, areola, asymptote, aureole, axis, beeline, bigness, body, bore, bottleneck, breadth, bulk, caliber, carry, chaplet, chord, circle, circuit, circumference, circus, closed circle, collision course, compass, concentralization, concentration, concourse, concurrence, confluence, conflux, congress, convergence, converging, corona, coronet, coverage, crossing, crown, cycle, depth, diadem, diagonal, diameter, diapason, diffusion, dimension, dimensions, direct line, directrix, discus, disk, dispersion, edge, emanation, eternal return, expanse, expansion, extension, extent, fairy ring, focalization, focus, funnel, gamut, garland, gauge, girth, glory, great-circle course, greatness, halo, height, hub, largeness, lasso, length, logical circle, loop, looplet, magic circle, magnitude, mass, measure, measurement, meeting, mutual approach, narrowing gap, noose, normal, orbit, perpendicular, proportion, proportions, purview, radiance, radiation, radius vector, range, ray, reach, register, right line, ring, rondelle, round, roundel, saucer, scale, scattering, scope, secant, segment, semidiameter, shortcut, side, size, spectrum, sphincter, spoke, spokes, spread, straight, straight course, straight line, straight stretch, straightaway, streamline, stretch, sweep, tangent, transversal, vector, vicious circle, volume, wheel, width, wreath