freq/mill – frequency per million

a number of occurrences (hits) of an item normalised per million. It is used to compare frequencies between corpora of different sizes.

number of hits : corpus size in millions of tokens = frequency per million

Example: A token found 10 times in a corpus of 1 million tokens will have a frequency per million equal to 10. A token found 100 times in a corpus of 100 million tokens will have a frequency per million equal to 1. The second token is less frequent.

see also

Statistics in Sketch Engine
Frequency per million
Average Reduced Frequency