|any real number that cannot be expressed as the ratio of two integers, such as π|
|irrational number (ĭ-rāsh'ə-nəl) Pronunciation Key
A number that cannot be expressed as a ratio between two integers and is not an imaginary number. If written in decimal notation, an irrational number would have an infinite number of digits to the right of the decimal point, without repetition. Pi and the square root of 2 (√2) are irrational numbers.