bloom filter

A Bloom filter is a space-efficient probabilistic data structure created by Burton Howard Bloom in 1970. Bloom filters are used to test whether an element is a member of a set. False positives are possible, but false negatives are not. In plain words, querying a bloom filter will let you know if an element is likely in a set or definitely not in a set.

https://en.wikipedia.org/wiki/Bloom_filter

---