n. [ Cf. F. diffraction. ] (Opt.) The deflection and decomposition of light in passing by the edges of opaque bodies or through narrow slits, causing the appearance of parallel bands or fringes of prismatic colors, as by the action of a grating of fine lines or bars. [ 1913 Webster ]

Remarked by Grimaldi (1665), and referred by him to a property of light which he called diffraction. Whewell. [ 1913 Webster ]

Diffraction grating. (Optics) See under Grating. --
Diffraction spectrum. (Optics) See under Spectrum. [ 1913 Webster ]

n. [ F. fraction, L. fractio a breaking, fr. frangere, fractum, to break. See Break. ] 1. The act of breaking, or state of being broken, especially by violence. [ Obs. ] [ 1913 Webster ]

Neither can the natural body of Christ be subject to any fraction or breaking up. Foxe. [ 1913 Webster ]

2. A portion; a fragment. [ 1913 Webster ]

Some niggard fractions of an hour. Tennyson. [ 1913 Webster ]

3. (Arith. or Alg.) One or more aliquot parts of a unit or whole number; an expression for a definite portion of a unit or magnitude. [ 1913 Webster ]

Common fraction, or
Vulgar fraction, a fraction in which the number of equal parts into which the integer is supposed to be divided is indicated by figures or letters, called the denominator, written below a line, over which is the numerator, indicating the number of these parts included in the fraction; as 1/2, one half, 2/5, two fifths. --
Complex fraction, a fraction having a fraction or mixed number in the numerator or denominator, or in both. Davies & Peck. --
Compound fraction, a fraction of a fraction; two or more fractions connected by of. --
Continued fraction,
Decimal fraction,
Partial fraction, etc. See under Continued, Decimal, Partial, etc. --
Improper fraction, a fraction in which the numerator is greater than the denominator. --
Proper fraction, a fraction in which the numerator is less than the denominator. [ 1913 Webster ]

v. t. (Chem.) To separate by means of, or to subject to, fractional distillation or crystallization; to fractionate; -- frequently used with out; as, to fraction out a certain grade of oil from pretroleum. [ 1913 Webster ]

a. 1. Of or pertaining to fractions or a fraction; constituting a fraction; as, fractional numbers. [ 1913 Webster ]

2. Relatively small; inconsiderable; insignificant; as, a fractional part of the population. [ 1913 Webster ]

Fractional crystallization (Chem.), a process of gradual and approximate purification and separation, by means of repeated solution and crystallization therefrom. --
Fractional currency, small coin, or paper notes, in circulation, of less value than the monetary unit. --
Fractional distillation (Chem.), a process of distillation so conducted that a mixture of liquids, differing considerably from each other in their boiling points, can be separated into its constituents. [ 1913 Webster ]

adv. By fractions or separate portions; as, to distill a liquid fractionally, that is, so as to separate different portions. [ 1913 Webster ]

a. Fractional. [ Obs. ] [ 1913 Webster ]

v. t. To separate (a mixture of chemical substances) into different portions or fractions, as in the distillation of liquids. [ 1913 Webster ]

n. the act or process of separating a mixture into portions of different composition, as in distillation or fractional crystallization.
Syn. -- fractional process. [ WordNet 1.5 +PJC ]

2. (Petroleum industry) Separation of crude oil into components of differing composition by fractional distillation. [ PJC ]

n. [ L. infractio: cf. F. infraction. ] The act of infracting or breaking; breach; violation; nonobservance; infringement; as, an infraction of a treaty, compact, rule, or law. I. Watts. [ 1913 Webster ]

n. [ F. réfraction. ] 1. The act of refracting, or the state of being refracted. [ 1913 Webster ]

2. The change in the direction of ray of light, heat, or the like, when it enters obliquely a medium of a different density from that through which it has previously moved. [ 1913 Webster ]

Refraction out of the rarer medium into the denser, is made towards the perpendicular. Sir I. Newton. [ 1913 Webster ]

3. (Astron.) (a) The change in the direction of a ray of light, and, consequently, in the apparent position of a heavenly body from which it emanates, arising from its passage through the earth's atmosphere; -- hence distinguished as atmospheric refraction, or astronomical refraction. (b) The correction which is to be deducted from the apparent altitude of a heavenly body on account of atmospheric refraction, in order to obtain the true altitude. [ 1913 Webster ]

Angle of refraction (Opt.), the angle which a refracted ray makes with the perpendicular to the surface separating the two media traversed by the ray. --
Conical refraction (Opt.), the refraction of a ray of light into an infinite number of rays, forming a hollow cone. This occurs when a ray of light is passed through crystals of some substances, under certain circumstances. Conical refraction is of two kinds; external conical refraction, in which the ray issues from the crystal in the form of a cone, the vertex of which is at the point of emergence; and internal conical refraction, in which the ray is changed into the form of a cone on entering the crystal, from which it issues in the form of a hollow cylinder. This singular phenomenon was first discovered by Sir W. R. Hamilton by mathematical reasoning alone, unaided by experiment. --
Differential refraction (Astron.), the change of the apparent place of one object relative to a second object near it, due to refraction; also, the correction required to be made to the observed relative places of the two bodies. --
Double refraction (Opt.), the refraction of light in two directions, which produces two distinct images. The power of double refraction is possessed by all crystals except those of the isometric system. A uniaxial crystal is said to be optically positive (like quartz), or optically negative (like calcite), or to have positive, or negative, double refraction, according as the optic axis is the axis of least or greatest elasticity for light; a biaxial crystal is similarly designated when the same relation holds for the acute bisectrix. --
Index of refraction. See under Index. --
Refraction circle (Opt.), an instrument provided with a graduated circle for the measurement of refraction. --
Refraction of latitude,
longitude,
declination,
right ascension, etc., the change in the apparent latitude, longitude, etc., of a heavenly body, due to the effect of atmospheric refraction. --
Terrestrial refraction, the change in the apparent altitude of a distant point on or near the earth's surface, as the top of a mountain, arising from the passage of light from it to the eye through atmospheric strata of varying density. [ 1913 Webster ]