Urban Dictionary: Rationalizing the Denominator

Top definition

The process of allowing a radical stuck in the denominator of a fraction to escape to the numerator—this is done by multiplying both parts of the fraction by a term containing the radical.

It's hard to know how big a number like 1/√2 is; however, rationalizing the denominator gives us a good idea: multiplying 1/√2 by √2/√2—which is the number 1—gives √2/2, which is about 1.4142 ÷ 2 = 0.7071.