So·lar, a.
 1. Of or pertaining to the sun; proceeding from the sun; as, the solar system; solar light; solar rays; solar influence. See Solar system, below.
 2. Astrol. Born under the predominant influence of the sun. [Obs.]
    And proud beside, as solar people are.   --Dryden.
 3. Measured by the progress or revolution of the sun in the ecliptic; as, the solar year.
 4. Produced by the action of the sun, or peculiarly affected by its influence.
    They denominate some herbs solar, and some lunar.   --Bacon.
 Solar cycle. See under Cycle.
 Solar day. See Day, 2.
 Solar engine, an engine in which the energy of solar heat is used to produce motion, as in evaporating water for a steam engine, or expanding air for an air engine.
 Solar flowers Bot., flowers which open and shut daily at certain hours.
 Solar lamp, an argand lamp.
 Solar microscope, a microscope consisting essentially, first, of a mirror for reflecting a beam of sunlight through the tube, which sometimes is fixed in a window shutter; secondly, of a condenser, or large lens, for converging the beam upon the object; and, thirdly, of a small lens, or magnifier, for throwing an enlarged image of the object at its focus upon a screen in a dark room or in a darkened box.

 Solar month. See under Month.
 Solar oil, a paraffin oil used an illuminant and lubricant.
 Solar phosphori Physics, certain substances, as the diamond, siulphide of barium (Bolognese or Bologna phosphorus), calcium sulphide, etc., which become phosphorescent, and shine in the dark, after exposure to sunlight or other intense light.
 Solar plexus Anat., a nervous plexus situated in the dorsal and anterior part of the abdomen, consisting of several sympathetic ganglia with connecting and radiating nerve fibers; -- so called in allusion to the radiating nerve fibers.
 Solar spots. See Sun spots, under Sun.
 Solar system Astron., the sun, with the group of celestial bodies which, held by its attraction, revolve round it. The system comprises the major planets, with their satellites; the minor planets, or asteroids, and the comets; also, the meteorids, the matter that furnishes the zodiacal light, and the rings of Saturn. The satellites that revolve about the major planets are twenty-two in number, of which the Earth has one (see Moon.), Mars two, Jupiter five, Saturn nine, Uranus four, and Neptune one. The asteroids, between Mars and Jupiter, thus far discovered (1900), number about five hundred, the first four of which were found near the beginning of the century, and are called Ceres, Pallas, Juno, and Vesta.
 -- Solar telegraph, telegraph for signaling by flashes of reflected sunlight.
 Solar time. See Apparent time, under Time.

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 Sun n.
 1. The luminous orb, the light of which constitutes day, and its absence night; the central body round which the earth and planets revolve, by which they are held in their orbits, and from which they receive light and heat. Its mean distance from the earth is about 92,500,000 miles, and its diameter about 860,000.
 Note: ☞ Its mean apparent diameter as seen from the earth is 32´ 4˝, and it revolves on its own axis once in 25⅓ days. Its mean density is about one fourth of that of the earth, or 1.41, that of water being unity.  Its luminous surface is called the photosphere, above which is an envelope consisting partly of hydrogen, called the chromosphere, which can be seen only through the spectroscope, or at the time of a total solar eclipse. Above the chromosphere, and sometimes extending out millions of miles, are luminous rays or streams of light which are visible only at the time of a total eclipse, forming the solar corona.
 2. Any heavenly body which forms the center of a system of orbs.
 3. The direct light or warmth of the sun; sunshine.
    Lambs that did frisk in the sun.   --Shak.
 4. That which resembles the sun, as in splendor or importance; any source of light, warmth, or animation.
    For the Lord God is a sun and shield.   --Ps. lxxiv. 11.
    I will never consent to put out the sun of sovereignity to posterity.   --Eikon Basilike.
 Sun and planet wheels Mach., an ingenious contrivance for converting reciprocating motion, as that of the working beam of a steam engine, into rotatory motion. It consists of a toothed wheel (called the sun wheel), firmly secured to the shaft it is desired to drive, and another wheel (called the planet wheel) secured to the end of a connecting rod. By the motion of the connecting rod, the planet wheel is made to circulate round the central wheel on the shaft, communicating to this latter a velocity of revolution the double of its own. --G. Francis.
 Sun angel Zool., a South American humming bird of the genus Heliangelos, noted for its beautiful colors and the brilliant luster of the feathers of its throat.
 Sun animalcute. Zool. See Heliozoa.
 Sun bath Med., exposure of a patient to the sun's rays; insolation.
 Sun bear Zool., a species of bear (Helarctos Malayanus) native of Southern Asia and Borneo. It has a small head and short neck, and fine short glossy fur, mostly black, but brownish on the nose. It is easily tamed. Called also bruang, and Malayan bear.
 Sun beetle Zool., any small lustrous beetle of the genus Amara.
 Sun bittern Zool., a singular South American bird (Eurypyga helias), in some respects related both to the rails and herons. It is beautifully variegated with white, brown, and black. Called also sunbird, and tiger bittern.
 Sun fever Med., the condition of fever produced by sun stroke.
 Sun gem Zool., a Brazilian humming bird (Heliactin cornutus). Its head is ornamented by two tufts of bright colored feathers, fiery crimson at the base and greenish yellow at the tip. Called also Horned hummer.
 Sun grebe Zool., the finfoot.
 Sun picture, a picture taken by the agency of the sun's rays; a photograph.
 Sun spots Astron., dark spots that appear on the sun's disk, consisting commonly of a black central portion with a surrounding border of lighter shade, and usually seen only by the telescope, but sometimes by the naked eye. They are very changeable in their figure and dimensions, and vary in size from mere apparent points to spaces of 50,000 miles in diameter. The term sun spots is often used to include bright spaces (called faculae) as well as dark spaces (called maculae). Called also solar spots. See Illustration in Appendix.
 Sun star Zool., any one of several species of starfishes belonging to Solaster, Crossaster, and allied genera, having numerous rays.
 Sun trout Zool., the squeteague.
 Sun wheel. Mach. See Sun and planet wheels, above.
 Under the sun, in the world; on earth. “There is no new thing under the sun.” --Eccl. i. 9.
 Note: ☞ Sun is often used in the formation of compound adjectives of obvious meaning; as, sun-bright, sun-dried, sun-gilt, sunlike, sun-lit, sun-scorched, and the like.