late 14c., originally in the mathematical sense, from AngloFrench fraccioun (Old French fraccion, 12c., "breaking") and directly from Late Latin fractionem (nominative fractio) "a breaking," especially into pieces, noun of action from past participle stem of Latin frangere "to break," from PIE root *bhreg "to break" (cf. Sanskrit (giri)bhraj "breakingforth (out of the mountains);" Gothic brikan, Old English brecan "to break;" Lithuanian brasketi "crash, crack;" Old Irish braigim "break" wind). Meaning "a breaking or dividing" is from early 15c.; sense of "broken off piece, fragment," is from c.1600.
fraction frac·tion (frāk'shən)
n.
An expression that indicates the quotient of two quantities.
A chemical component separated by fractionation.
A disconnected piece; a fragment.
An aliquot portion or any portion.
fraction (frāk'shən)

A mathematical expression representing the division of one whole number by another. Usually written as two numbers separated by a horizontal or diagonal line, fractions are also used to indicate a part of a whole number or a ratio between two numbers. Fractions may have a value of less than one, as with 1/2, or equal to one, as with 2/2, or more than one, as with 3/2. The top number of a fraction is the numerator and the bottom number is the denominator.