focus English · revision 2048

+ ==Pronunciation==

+ * IPA: /ˈfəʊ̯.kəs/ ''(UK)''; /ˈfoʊ̯.kəs/ ''(US)''^(Wiktionary)

+

+ ==Etymology==

+ It is [[bor|la-new|focus|t=central point]],^(Barnhart 1995)^(MW Collegiate) from [[la|focus|t=hearth, fireplace]],^(AHD)^(Barnhart 1995)^(Etymonline)^(MW Collegiate)^(RHWU) which is of unknown origin.^(Etymonline)

+

+ ==Earliest recorded meaning==

+ A point at which rays meet (1644, of sound waves in Barnhart).^(Barnhart 1995)^(MW Collegiate)^(Etymonline)

+

+ ==Semantic evolution==

+ In post-classical Latin ''focus'' was used for the fire itself.^(Etymonline) Kepler used it in 1604 for a point of convergence in mathematics, probably by analogy with the burning point of a lens, where the heat rays meet.^(Etymonline)^(Barnhart 1995) Hobbes introduced it into English in the 1650s,^(Etymonline) and in geometry it names a point that defines a curve such as an ellipse (1656).^(OED 1989) The figurative sense of a centre of activity or interest is first recorded in 1796.^(Barnhart 1995)^(Etymonline) The verb (1775) first meant to bring into focus in optics;^(Barnhart 1995)^(Etymonline)^(OED 1989)^(MW Collegiate) the figurative “to concentrate attention” is from 1807.^(Etymonline)^(OED 1989)

+

+ ==Timeline==

+ * 1604 – used by Kepler in its mathematical sense.^(Etymonline)

+ * 1644 – a point where rays meet.^(Barnhart 1995)^(MW Collegiate)

+ * 1656 – in geometry, a point defining a curve.^(OED 1989)

+ * 1693 – ''focal''.^(Barnhart 1995)

+ * 1775 – verb, to bring into focus.^(OED 1989)^(Barnhart 1995)^(MW Collegiate)

+ * 1796 – a centre of activity.^(Barnhart 1995)^(Etymonline)

+ * 1807 – verb, figurative, to concentrate.^(OED 1989)^(Etymonline)

+

+ ==Modern meaning==

+ ===Noun===

+ # A centre of interest, activity or attention.^(AHD)^(MW Collegiate)^(RHWU)^(Wiktionary)

+ # Close or narrow attention; concentration.^(AHD)^(Wiktionary)

+ # ''(physics)'' A point at which rays of light, heat or sound meet, or from which they appear to spread.^(AHD)^(MW Collegiate)^(RHWU)^(Wiktionary)

+ # The clear and sharp condition of an image, or the adjustment that produces it.^(AHD)^(MW Collegiate)^(RHWU)^(Wiktionary)

+ # ''(geometry)'' A fixed point used to define a conic section.^(MW Collegiate)^(Wiktionary)

+ # The point underground where an earthquake starts.^(Wiktionary)

+

+ ===Verb===

+ # To concentrate attention or effort.^(AHD)^(MW Collegiate)^(RHWU)^(Wiktionary)

+ # To adjust a lens or the eyes to give a clear image.^(AHD)^(MW Collegiate)^(RHWU)^(Wiktionary)

+ # To cause light or other rays to converge.^(AHD)^(MW Collegiate)^(RHWU)^(Wiktionary)

+

+ ==Word family==

+ * [[focuser]]

+ * [[focusable]]

+ * [[autofocus]]

+ * [[overfocus]]

+ * [[prefocus]]

+ * [[defocus]]

+ * [[misfocus]]

+

+ ==Related words==

+ * [[focal]]

+ * [[foyer]]

+ * [[fuel]]

+ * [[curfew]]

+

+ ==References==

+ {{reflist}}