(At`mos*phe*rol"o*gy) n. [Atmosphere + -logy.] The science or a treatise on the
(At"o*kous) a. [Gr. barren; 'a priv. + offspring.] (Zoöl.) Producing only asexual individuals, as
the eggs of certain annelids.
(A*toll") n. [The native name in the Indian Ocean.] A coral island or islands, consisting of a belt
of coral reef, partly submerged, surrounding a central lagoon or depression; a lagoon island.
(At"om) n. [L. atomus, Gr. uncut, indivisible; 'a priv. + verbal adj. of to cut: cf. F. atome. See
1. (Physics) (a) An ultimate indivisible particle of matter. (b) An ultimate particle of matter not necessarily
indivisible; a molecule. (c) A constituent particle of matter, or a molecule supposed to be made up of
These three definitions correspond to different views of the nature of the ultimate particles of matter. In
the case of the last two, the particles are more correctly called molecules. Dana.
2. (Chem.) The smallest particle of matter that can enter into combination; one of the elementary constituents
of a molecule.
3. Anything extremely small; a particle; a whit.
There was not an atom of water.
Sir J. Ross.
(At"om), v. t. To reduce to atoms. [Obs.] Feltham.
(A*tom"ic A*tom"ic*al) a. [Cf. F. atomique.]
1. Of or pertaining to atoms.
2. Extremely minute; tiny.
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.
(A*tom"ic*al*ly), adv. In an atomic manner; in accordance with the atomic philosophy.
(At`o*mi"cian) n. An atomist. [R.]
(A*tom"i*cism) n. Atomism. [Obs.]
(At`o*mic"i*ty) n. [Cf. F. atomicité.] (Chem.) Degree of atomic attraction; equivalence; valence; also
(a later use) the number of atoms in an elementary molecule. See Valence.
(At"om*ism) n. [Cf. F. atomisme.] The doctrine of atoms. See Atomic philosophy, under
(At"om*ist), n. [Cf. F. atomiste.] One who holds to the atomic philosophy or theory. Locke.