Ratio /(rā"shĭ*ō̇ [or] rā"shō̇)/

Ra·ti·o

Ratio

n.
  1. The relation which one quantity or magnitude has to another of the same kind. It is expressed by the quotient of the division of the first by the second; thus, the ratio of 3 to 6 is expressed by a to b by a/b; or (less commonly) the second term is made the dividend; as, a:b = b/a. (Math.)
  2. Hence, fixed relation of number, quantity, or degree; rate; proportion; as, the ratio of representation in Congress.

Phrases & Compounds
Compound ratio
See under Compound, Duplicate, etc.
Ratio of a geometrical progression
the constant quantity by which each term is multiplied to produce the succeeding one.