re·duc·tion 
(rĭ-dŭkshən)
(rĭ-dŭkshən)n.
1. The act or process of reducing.
2. The result of reducing: a reduction in absenteeism.
3. The amount by which something is lessened or diminished: a reduction of 12 percent in violent crime.
4. A sauce that has been thickened or concentrated by boiling.
5. Biology The first meiotic division, in which the chromosome number is reduced from diploid to haploid. Also called reduction division.
6. Chemistry
a. A decrease in positive valence or an increase in negative valence by the gaining of electrons.
b. A reaction in which hydrogen is combined with a compound.
c. A reaction in which oxygen is removed from a compound.
7. Mathematics
a. The canceling of common factors in the numerator and denominator of a fraction.
b. The converting of a fraction to its decimal equivalent.
c. The converting of an expression or equation to its simplest form.
[Middle English reduccioun, restoration, action of bringing back to a former state, from Middle French reduction, from Old French redution, from Latin reductiō, reductiōn-, from reductus, past participle of redūcere, to bring back; see REDUCE.]
re·duction·al adj.