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An ordered list of values, all stored under one name.
An ordered, indexable collection of values. Most languages provide methods to push, pop, slice, map, and filter. Access by index is O(1); insertion in the middle is O(n).
A contiguous block of memory holding fixed-size elements (in compiled languages) or a dynamic resizable structure with amortized O(1) append (in dynamic languages). JavaScript arrays are sparse hashmaps that engines optimize into dense storage when access patterns allow.