The Collaborative International Dictionary of English v.0.48:

Fraction \Frac"tion\, 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.]
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            Neither can the natural body of Christ be subject to
            any fraction or breaking up.          --Foxe.
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   2. A portion; a fragment.
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            Some niggard fractions of an hour.    --Tennyson.
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   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.
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   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.
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The Collaborative International Dictionary of English v.0.48:

Proper \Prop"er\, a. [OE. propre, F. propre, fr. L. proprius.
   Cf. Appropriate.]
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   1. Belonging to one; one's own; individual. "His proper good"
      [i. e., his own possessions]. --Chaucer. "My proper son."
      --Shak.
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            Now learn the difference, at your proper cost,
            Betwixt true valor and an empty boast. --Dryden.
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   2. Belonging to the natural or essential constitution;
      peculiar; not common; particular; as, every animal has his
      proper instincts and appetites.
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            Those high and peculiar attributes . . . which
            constitute our proper humanity.       --Coleridge.
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   3. Befitting one's nature, qualities, etc.; suitable in all
      respect; appropriate; right; fit; decent; as, water is the
      proper element for fish; a proper dress.
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            The proper study of mankind is man.   --Pope.
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            In Athens all was pleasure, mirth, and play,
            All proper to the spring, and sprightly May.
                                                  --Dryden.
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   4. Becoming in appearance; well formed; handsome. [Archaic]
      "Thou art a proper man." --Chaucer.
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            Moses . . . was hid three months of his parents,
            because they saw he was a proper child. --Heb. xi.
                                                  23.
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   5. Pertaining to one of a species, but not common to the
      whole; not appellative; -- opposed to common; as, a
      proper name; Dublin is the proper name of a city.
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   6. Rightly so called; strictly considered; as, Greece proper;
      the garden proper.
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   7. (Her.) Represented in its natural color; -- said of any
      object used as a charge.
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   In proper, individually; privately. [Obs.] --Jer. Taylor.


   Proper flower or Proper corolla (Bot.), one of the single
      florets, or corollets, in an aggregate or compound flower.


   Proper fraction (Arith.) a fraction in which the numerator
      is less than the denominator.

   Proper nectary (Bot.), a nectary separate from the petals
      and other parts of the flower. -- Proper noun (Gram.), a
      name belonging to an individual, by which it is
      distinguished from others of the same class; -- opposed to
      common noun; as, John, Boston, America.

   Proper perianth or Proper involucre (Bot.), that which
      incloses only a single flower.

   Proper receptacle (Bot.), a receptacle which supports only
      a single flower or fructification.
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WordNet (r) 3.0 (2006):

proper fraction
    n 1: a fraction with a numerator smaller than the denominator