Meaning of ratio test

ra'tio test"

Pronunciation: [key]
— Math. Math.
  1. the theorem that a given infinite series converges if the absolute value of the ratio of the term succeeding the nth term to the nth term approaches a limit less than 1 as n increases without bound.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.