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,

In the early 1970s, engineers listening for Russian submarines started detecting strange underwater signals. Using hydrophones (underwater microphones), they repeatedly picked up rhythmic, varying sounds.

The sounds that make up humpback whale songs follow some of the same statistical rules seen in human languages, which may be because of how they are learned