ratio and proportion

ratio:

A ratio is a comparison of two numbers. We generally separate the two numbers in the ratio with a colon (:). Suppose we want to write the ratio of 8 and 12.
We can write this as 8:12 or as a fraction 8/12, and we say the ratio is eight to twelve.

proportion:

  Four quantities a, b, c and d are said to be in proportion, if a:b=c:d.