| 释义 |
ellipse|ɛˈlɪps|
[ad. Gr. ἔλλειψις, n. of action f. ἐλλείπειν to come short. (In the case of the ellipse regarded as a conic section the inclination of the cutting plane to the base ‘comes short of’, as in the case of the hyperbola it exceeds, the inclination of the side of the cone.)
Not in Johnson, Todd, or Richardson (1836); for early examples of the pl. ellipses see ellipsis.]
1. A plane closed curve (in popular language a regular oval), which may be defined in various ways:
a. Considered as a conic section; the figure produced when a cone is cut obliquely by a plane making a smaller angle with the base than the side of the cone makes with the base.
b. A curve in which the sum of the distances of any point from the two foci is a constant quantity.
c. A curve in which the focal distance of any point bears to its distance from the directrix a constant ratio smaller than unity.
The planetary orbits being (approximately) elliptical, ellipse is sometimes used for ‘orbit’ (of a planet).
1753Chambers Cycl. Supp. s.v. Ellipsis, [The form ellipse is used throughout; the Cycl. 1751 has only ellipsis]. 1815Hutton Math. Dict., Ellipse or Ellipsis. 1842Tennyson Golden Year 24 The dark Earth follows wheel'd in her ellipse. 1868Lockyer Heavens (ed. 3) 120 A circle seen obliquely or perspectively shows the form of an ellipse. 1880C. & F. Darwin Movem. Pl. 1 Other irregular ellipses..are successively described.
2. transf. An object or figure bounded by an ellipse. Also fig.
1857Bullock tr. Cazeaux's Midwif. 29 The abdominal strait has been..compared to an ellipse. 1869Dunkin Midn. Sky 163 An ellipse of small stars.
3. Gram. = ellipsis 2. Somewhat rare.
1843–83Liddell & Scott Gr. Lex. s.v. Ἔλλειψις. 1886 Roby Lat. Gram. II (ed. 5) 511 (Index). |