Evolutionary condition of language has been put in this book. The condition is: When a voice code (example consonant /k/) necessarily needs voice code (example vowel /i/) for the production of human voice (example /ki/)...[note that no one can speak consonant /k/ without the vowel], only then single voice codes in human voice are producible and only then humans can reproduce the same sound. The above evolutionary condition is true for recursion and memory. Note that it is not only evolutionary condition but also entropy which forms language. Other characteristics are environment, multiple things and co-efficiency. So condition, entropy and other characteristics are the reason behind language. Human Voice sequences are understood for communication, language and thinking by humans but there can be other unknown functions too.