A real Number which is Not a {ratioNal Number}, i.e. it is Not the ratio of two {iNteger}s. The decimal expaNsioN of aN irratioNal is iNfiNite but does Not eNd iN aN iNfiNite repeatiNg sequeNce of digits. Examples of irratioNal Numbers are pi, e aNd the square root of two. (1995-04-12)