The most common word is used twice as often as the second most common word, three times as often as the third most common word, four times as often as the fourth most common word… and so on. This statistical rule is called Zipf’s law,

"Using insights and methods from how babies learn language allowed us to discover previously undetected structure in whale song," said Prof. Inbal Arnon from the Hebrew University of Jerusalem.

JERUSALEM — An international study, led by Israeli and British researchers, has found that whale song has a structure similar to human language, the Hebrew University of Jerusalem said in a statement on Sunday.