radius English · revision 15403

+ {{infobox|confidence=established|formation=borrowing|attested=1578|origins=la radius}}

+

+ ==Pronunciation==

+ * IPA: /ˈɹeɪ.di.əs/^(Wiktionary)

+

+ ==Etymology==

+ It is [[bor|la|radius|t=staff, rod; spoke of a wheel; ray of light]],^(Barnhart 1988)^(Etymonline)^(Hoad 1986) a word of unknown origin,^(Etymonline) perhaps related to [[m|la|rādīx|t=root]], though de Vaan finds that unlikely.^(Etymonline) It is a doublet of [[ray]].^(Barnhart 1988)

+

+ ==Earliest recorded meaning==

+ The staff of a cross-staff, a straight rod: 1597 in Barnhart and the OED, the 1590s in Etymonline;^(Barnhart 1988)^(OED 1989)^(Etymonline) Merriam-Webster dates a sense to 1578.^(MWU 2024)

+

+ ==Semantic evolution==

+ As the shorter bone of the forearm it is from 1615 (the 1610s), as in Latin.^(OED 1989)^(Etymonline)^(Hoad 1986) The geometric sense, a line from the centre of a circle to the circumference, is first recorded in Hobbes's ''Six Lessons'' (1656),^(Barnhart 1988)^(Etymonline) and a circular area of a given distance around a place from 1853.^(Etymonline) The classical plural is ''radii''.^(Etymonline)^(Collins 2023) The verb, to round off a corner, is from 1938.^(OED 1989)

+

+ ==Timeline==

+ * 1578 – radius (Merriam-Webster).^(MWU 2024)

+ * 1597 – the staff of a cross-staff.^(Barnhart 1988)^(OED 1989)

+ * 1615 – the forearm bone.^(OED 1989)

+ * 1656 – the radius of a circle.^(Barnhart 1988)

+ * 1853 – a circular area.^(Etymonline)

+

+ ==Modern meaning==

+ ===Noun===

+ # A straight line from the centre of a [[circle]] or [[sphere]] to its edge, or its length.^(AHD)^(Collins 2023)

+ # A circular area within a given distance of a place: ''within a ten-mile radius''.^(AHD)

+ # ''(anatomy)'' The shorter, thicker of the two bones of the [[forearm]].^(AHD)^(Collins 2023)

+

+ ==Word family==

+ * [[circumradius]]

+ * [[inradius]]

+ * [[triradius]]

+ * [[Bohr radius]]

+ * [[hydraulic radius]]

+ * [[radius of convergence]]

+ * [[radius of curvature]]

+

+ ==Related words==

+ * [[radial]]

+ * [[radiate]]

+ * [[radiation]]

+ * [[ray]]

+ * [[radiant]]

+ * [[radio]]

+

+ ==References==

+ {{reflist}}