I believe that an irrational number is one that cannot be written exactly - such as pi, which has been calculated to several million decimal places, but still goes on (and on and on and on).
A rational number is one which can be written as a ratio
ie 1/3 or 6/10 or logically 4/1
Pi cannot be written as a ratio (although it is close to 22/7 but not exactly that) and is therefore an irrational number.
why thank you park your more then welcome. if i see a question i know the answer to has already been answered then if i can i try to stick a funny one in if i can, see the music section for examples!