tropic of cancer
 北回歸線


 Trop·ic, n.
 1. Astron. One of the two small circles of the celestial sphere, situated on each side of the equator, at a distance of 23° 28´, and parallel to it, which the sun just reaches at its greatest declination north or south, and from which it turns again toward the equator, the northern circle being called the Tropic of Cancer, and the southern the Tropic of Capricorn, from the names of the two signs at which they touch the ecliptic.
 2. Geog. (a) One of the two parallels of terrestrial latitude corresponding to the celestial tropics, and called by the same names. (b) pl. The region lying between these parallels of latitude, or near them on either side.
    The brilliant flowers of the tropics bloom from the windows of the greenhouse and the saloon.   --Bancroft.


 Can·cer n.
 1. Zool. A genus of decapod Crustacea, including some of the most common shore crabs of Europe and North America, as the rock crab, Jonah crab, etc. See Crab.
 2. Astron. (a) The fourth of the twelve signs of the zodiac. The first point is the northern limit of the sun's course in summer; hence, the sign of the summer solstice. See Tropic. (b) A northern constellation between Gemini and Leo.
 3. Med. Formerly, any malignant growth, esp. one attended with great pain and ulceration, with cachexia and progressive emaciation. It was so called, perhaps, from the great veins which surround it, compared by the ancients to the claws of a crab. The term is now restricted to such a growth made up of aggregations of epithelial cells, either without support or embedded in the meshes of a trabecular framework.
 Note: ☞ Four kinds of cancers are recognized: (1) Epithelial cancer, or Epithelioma, in which there is no trabecular framework. See Epithelioma. (2) Scirrhous cancer, or Hard cancer, in which the framework predominates, and the tumor is of hard consistence and slow growth. (3) Encephaloid  cancer, Medullary  cancer, or Soft cancer, in which the cellular element predominates, and the tumor is soft, grows rapidy, and often ulcerates. (4) Colloid cancer, in which the cancerous structure becomes gelatinous. The last three varieties are also called carcinoma.
 Cancer cells, cells once believed to be peculiar to cancers, but now know to be epithelial cells differing in no respect from those found elsewhere in the body, and distinguished only by peculiarity of location and grouping.
 Cancer root Bot., the name of several low plants, mostly parasitic on roots, as the beech drops, the squawroot, etc.
 Tropic of Cancer. See Tropic.

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 Tropic of Cancer
      n : a line of latitude about 23 degrees North of the equator