# radius
## English
### Etymology

Borrowed from Latin radius (“ray”). Doublet of ray.

### Pronunciation

* enPR: rā'-dē-əs, IPA: /ˈɹeɪ.di.əs/
* Audio (US):(file)
* Rhymes: -eɪdiəs
* Hyphenation: ra‧di‧us

### Noun

radius (plural radii or radiuses)
* (anatomy) The long bone in the forearm, on the side of the thumb.
** 1808, John Barclay, The Muscular Motions of the Human Body‎, →OCLC, page 396:It is also obvious, and proved by experiment, that the rotatory motions observed in the hand proceed from the rotatory motions of the radius.
* (zoology) The lighter bone (or fused portion of bone) in the forelimb of an animal.
* (entomology) One of the major veins of the insect wing, between the subcosta and the media; the vein running along the costal edge of the discal cell.
* (geometry) A line segment between any point of a circle or sphere and its center.
    Fatima claims to have visited all the bars within a five-mile radius of her Manhattan apartment.
** 1994, Viacheslav V. Nikulin, Igor R. Shafarevich, translated by Miles Reid, Geometries and Groups, Springer, page 194:We start with spherical geometries. The two geometries on spheres of radiuses R$_1$ and R$_2$ are obviously identical if R$_1$ = R$_2$; moreover, the converse also holds.
** 2016, Jubee Sohn, Ho Seong Hwang, Margaret J. Geller, Antonaldo Diaferio, Kenneth J. Rines, Myung Gyoon Lee, Gwang-Ho Lee, “Compact Groups of Galaxies with Complete Spectroscopic Redshifts in the Local Universe”, in JKAS‎, volume 2015:The velocity dispersions of early- and late-type galaxies in compact groups change little with groupcentric radius; the radii sampled are less than $100~h^{-1}$ kpc, smaller than the radii typically sampled by members of massive clusters of galaxies.
* (geometry) The length of this line segment.
** 1998, Dieter Schuocker, Handbook of the Eurolaser Academy, Springer Science & Business Media, →ISBN, page 51:This contribution reduces with increasing distance p from the emitting surface element dA, due to conservation of energy, as the wave energy distributed across the spherical wave front remains constant, while the radius increases during ...
* Anything resembling a radius, such as the spoke of a wheel, the movable arm of a sextant, or one of the radiating lines of a spider's web.
** 1674, Robert Hooke, Animadversions on the Firſt Part of the Machina Coelestis of the […] Aſtronomer Johannes Hevelius […] ‎, page 43:[…] I can do more with a Quadrant, Sextant or Octant, of 1 foot Radius, furniſhed with Teleſcopical Sights and Screws, then can poſſibly be done with any other Inſtrument, furniſhed only with Common Sights, though 10, 20, 30, nay threeſcore foot Radius; […]
* (graph theory) The minimum eccentricity of any vertex, for a given graph.

#### Synonyms

* (vein of insect wing): R

#### Derived terms

* Bohr radius
* Debye radius
* Earth radius
* hydraulic radius
* potato radius
* radius arm
* radius bar
* radius of action
* radius of convergence
* radius of curvature
* radius of gyration
* radius rod
* radius vector
* Schwarzschild radius
* sight radius
* van der Waals radius

#### Related terms

* radial
* radiad
* radiate, radiation

#### Translations
### Verb

radius (third-person singular simple present radiuses, present participle radiusing, simple past and past participle radiused)
* (transitive) To give a rounded edge to.
** 2014, Anil Mital, Anoop Desai, Anand Subramanian, Product Development, page 358:A comfortable grip is ensured by smoothing the surface of the handle and radiusing the edge.

### See also

* ulna
* semidiameter
* Radius on Wikipedia.Wikipedia
* Radius (bone) on Wikipedia.Wikipedia

### Anagrams

* Darius

## Crimean Tatar

Other scripts :
| Cyrillic | радиус |
| Roman | |

### Etymology

Borrowed from Russian радиус (radius), from Latin radius.

### Noun

radius
* radius (line segment or length of this line segment)

#### Declension
### References

* Mirjejev, V. A., Usejinov, S. M. (2002) Ukrajinsʹko-krymsʹkotatarsʹkyj slovnyk [Ukrainian – Crimean Tatar Dictionary]‎, Simferopol: Dolya, →ISBN
* “radius”, in Luğatçıq (in Russian)

## Danish
### Etymology

Borrowed from Latin radius.

### Noun

radius c (singular definite radien or radiusen, plural indefinite radier or radiuser)
* (geometry) radius

### References

* “radius” in Den Danske Ordbog

## Esperanto
### Verb

radius
* conditional of radii

## Faroese
### Noun

radius m (genitive singular radius, plural radiusar)
* (geometry) radius

#### Declension
## French
### Etymology

Borrowed from Latin radius. Doublet of rai, which was inherited.

### Pronunciation

* IPA: /ʁa.djys/
* Audio:(file)

### Noun

radius m (plural radius)
* (anatomy) radius

### Further reading

* “radius”, in Trésor de la langue française informatisé [Digitized Treasury of the French Language], 2012.

### Anagrams

* durais

## Ido
### Verb

radius
* conditional of radiar

## Indonesian
### Etymology

Learned borrowing from Latin radius.

### Pronunciation

* IPA: /raˈdiʊs/
* Hyphenation: ra‧di‧us

### Noun

radius (uncountable)
* radius:
** (mathematics) a line segment between any point of a circle or sphere and its center; the length of this line segment.
    Synonym: jari-jari
** (anatomy) the long bone in the forearm, on the side of the thumb.
    Synonym: pengumpil
* area of a circle, commonly with epicenter as center.

#### Derived terms

* radius pelayaran

### Further reading

* “radius” in Kamus Besar Bahasa Indonesia, Jakarta: Agency for Language Development and Cultivation – Ministry of Education, Culture, Research, and Technology of the Republic of Indonesia, 2016.

## Latin
### Etymology

Of uncertain origin. Some connect it with rādīx and rāmus. Tucker suggests Proto-Indo-European *neredʰ- (“extend forth, rise, outward”) akin to Sanskrit वर्धते (vardhate, “rise, grow”), or from Ancient Greek ἄρδις (árdis, “sharp point”). May ultimately be from Proto-Indo-European *reh₁t- (“bar, beam, stem”).

### Pronunciation

* (Classical Latin) IPA: /ˈra.di.us/, [ˈräd̪iʊs̠]
* (modern Italianate Ecclesiastical) IPA: /ˈra.di.us/, [ˈräːd̪ius]

### Noun

radius m (genitive radiī or radī); second declension
* a staff, rod
** a spoke of a wheel
** a rod for measurement
** the radius of a circle; a rotating radial arm
** (weaving) a shuttle
** (poetic) a bolt or shaft
** the spur of a bird's leg
** the tail-spine of a stingray
** (anatomy) the radius (the outer bone of a forearm)
* a ray of light (also reflected)
** 29 BCE – 19 BCE, Virgil, Aeneid 4.118-119:“[...] ubi prīmōs crāstinus ortus extulerit Tītān, radiīsque retēxerit orbem.”“[...] when at tomorrow’s early dawn the Titan [Sun] will have risen, and with [his] rays revealed the world.”
** 8 CE, Ovid, Fasti 6.717:At pater Hēliadum radiōs ubi tīnxerit undīsBut when the father of the Heliades shall have dipped his rays in the waves [...]. (The father is the sun god; see: Heliades.)
** (according to an ancient theory of vision) a ray extending from the eye to the object seen
* the name of an elongated variety of olive
* the name of a rod with which geometers make figures in dust, also known as a virga

#### Declension

Second-declension noun.
$^1$Found in older Latin (until the Augustan Age).

#### Derived terms

* radiō
* radiolus

#### Descendants

* → Albanian: rreze
* Aromanian: aradzã, radzã
* Catalan: raig
** →? Sardinian: raxu
* Dalmatian: rus, ruaz
* Old French: rai
** French: rai
** → English: ray
* Friulian: rai
* Galician: raia, raio, raxo
* Italian: raggio
** Sicilian: raggiu (italianized, palatalized variant)
* Mirandese: raio
* Mozarabic: ראיה (rʔyh)
* Occitan: rai
* Portuguese: raia, raio
* Romanian: rază
* Sardinian: (ar)raju, (ar)rag(g)iu, arràciu, ràdiu
* Sicilian: raja
* Spanish: raya, rayo, raza
** → Sardinian: razu m, raza f, rasu
* Venetan: rajo
* → Welsh: rhaidd

##### Learned borrowings

* → Catalan: radi
* → Italian: radio
* → English: radius, radio-, radio
* → French: radius
* → Galician: radio
* → German: Radius
* → Portuguese: rádio
* → Romanian: radius
* → Russian: ра́диус (rádius)
* → Sicilian: ràdiu
* → Spanish: radio

### References

* ↑ De Vaan, Michiel (2008) “radius”, in Etymological Dictionary of Latin and the other Italic Languages (Leiden Indo-European Etymological Dictionary Series; 7), Leiden, Boston: Brill, →ISBN, page 512
* ↑ Tucker, T.G., Etymological Dictionary of Latin, Ares Publishers, 1976 (reprint of 1931 edition).

### Further reading

* “radius” on page 1731 of the Oxford Latin Dictionary (2nd ed., 2012)
* “radius”, in Charlton T. Lewis and Charles Short (1879) A Latin Dictionary, Oxford: Clarendon Press
* “radius”, in Charlton T. Lewis (1891) An Elementary Latin Dictionary, New York: Harper & Brothers
* "radius", in Charles du Fresne du Cange’s Glossarium Mediæ et Infimæ Latinitatis (augmented edition with additions by D. P. Carpenterius, Adelungius and others, edited by Léopold Favre, 1883–1887)
* radius in Gaffiot, Félix (1934) Dictionnaire illustré latin-français, Hachette.
* “radius”, in Harry Thurston Peck, editor (1898), Harper's Dictionary of Classical Antiquities, New York: Harper & Brothers
* “radius”, in William Smith et al., editor (1890), A Dictionary of Greek and Roman Antiquities, London: William Wayte. G. E. Marindin

## Norwegian Bokmål
### Etymology

Borrowed from Latin radius.

### Noun

radius m (definite singular radien or radiusen, indefinite plural radier, definite plural radiene)
* (geometry) radius

### References

* “radius” in The Bokmål Dictionary.

## Norwegian Nynorsk
### Etymology

Borrowed from Latin radius.

### Noun

radius m (definite singular radiusen, indefinite plural radiusar, definite plural radiusane)
* (geometry) radius

### References

* “radius” in The Nynorsk Dictionary.

## Romanian
### Etymology

Borrowed from French radius, Latin radius. Compare the inherited doublet rază (“ray”).

### Noun

radius n (plural radiusuri)
* (anatomy) radius (bone)

#### Related terms

* radiu