text: where's "random" concept coming from? and how to generate and "truly random" number? randomness, or complete unpredictability, in different fields have different meaning and significance.   many scientific fields are concerned with randomness:  algorithmic probability  chaos theory  cryptography  game theory  information theory  pattern recognition  probability theory  quantum mechanics  statistics  statistical mechanics  (you can read about this in the first link)  imho, there is no way to generate truly random numbers if you are thinking of generating millions of numbers (in any large data set, one is sure to find some kind of statistical pattern). the closest we can get to complete randomness is a hardware pseudorandom process (see second and third link).