Amortized cost is a technical term in complexity analysis: https://en.wikipedia.org/wiki/Amortized_analysis https://en.wikipedia.org/wiki/Amortized_analysis If

Amortized cost is a technical term in complexity analysis: https://en.wikipedia.org/wiki/Amortized_analysis https://en.wikipedia.org/wiki/Amortized_analysis If you use the terminology precisely, the worst case cost of a regular hash table insertion is O(n) because of the potential resize, but its amortized cost is O(1) because that's what it "averages out to".