atomic weight
 原子量


 atomic weight 名詞
 原子量


 Weight n.
 1. The quality of being heavy; that property of bodies by which they tend toward the center of the earth; the effect of gravitative force, especially when expressed in certain units or standards, as pounds, grams, etc.
 Note: ☞ Weight differs from gravity in being the effect of gravity, or the downward pressure of a body under the influence of gravity; hence, it constitutes a measure of the force of gravity, and being the resultant of all the forces exerted by gravity upon the different particles of the body, it is proportional to the quantity of matter in the body.
 2. The quantity of heaviness; comparative tendency to the center of the earth; the quantity of matter as estimated by the balance, or expressed numerically with reference to some standard unit; as, a mass of stone having the weight of five hundred pounds.
 For sorrow, like a heavy-hanging bell,
 Once set on ringing, with his own weight goes.   --Shak.
 3. Hence, pressure; burden; as, the weight of care or business.  “The weight of this said time.”
    For the public all this weight he bears.   --Milton.
    [He] who singly bore the world's sad weight.   --Keble.
 4. Importance; power; influence; efficacy; consequence; moment; impressiveness; as, a consideration of vast weight.
    In such a point of weight, so near mine honor.   --Shak.
 5. A scale, or graduated standard, of heaviness; a mode of estimating weight; as, avoirdupois weight; troy weight; apothecaries' weight.
 6. A ponderous mass; something heavy; as, a clock weight; a paper weight.
    A man leapeth better with weights in his hands.   --Bacon.
 7. A definite mass of iron, lead, brass, or other metal, to be used for ascertaining the weight of other bodies; as, an ounce weight.
 8. Mech. The resistance against which a machine acts, as opposed to the power which moves it.  [Obs.]
 Atomic weight. Chem. See under Atomic, and cf. Element.
 Dead weight, Feather weight, Heavy weight, Light weight, etc.  See under Dead, Feather, etc.
 Weight of observation Astron. & Physics, a number expressing the most probable relative value of each observation in determining the result of a series of observations of the same kind.
 Syn: -- Ponderousness; gravity; heaviness; pressure; burden; load; importance; power; influence; efficacy; consequence; moment; impressiveness.


 A·tom·ic A·tom·ic·al a.
 1. Of or pertaining to atoms.
 2. Extremely minute; tiny.
 Atomic bomb, see atom bomb in the vocabulary.
 Atomic philosophy, or Doctrine of atoms, a system which, assuming that atoms are endued with gravity and motion, accounted thus for the origin and formation of all things. This philosophy was first broached by Leucippus, was developed by Democritus, and afterward improved by Epicurus, and hence is sometimes denominated the Epicurean philosophy.
 Atomic theory, or the Doctrine of definite proportions Chem., teaches that chemical combinations take place between the supposed ultimate particles or atoms of bodies, in some simple ratio, as of one to one, two to three, or some other, always expressible in whole numbers.
 Atomic weight Chem., the weight of the atom of an element as compared with the weight of the atom of hydrogen, taken as a standard.

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 Com·bine, v. i.
 1. To form a union; to agree; to coalesce; to confederate.
 You with your foes combine,
 And seem your own destruction to design   --Dryden.
    So sweet did harp and voice combine.   --Sir W. Scott.
 2. To unite by affinity or natural attraction; as, two substances, which will not combine of themselves, may be made to combine by the intervention of a third.
 3. Card Playing In the game of casino, to play a card which will take two or more cards whose aggregate number of pips equals those of the card played.
 Combining weight Chem., that proportional weight, usually referred to hydrogen as a standard, and for each element fixed and exact, by which an element unites with another to form a distinct compound. The combining weights either are identical with, or are multiples or submultiples of, the atomic weight. See Atomic weight, under Atomic, a.

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 atomic weight
      n : (chemistry) the ratio of the atomic mass of an element to
          half the atomic mass of carbon-12 [syn: {relative atomic
          mass]