In other contexts, an array might mean another one of the implementations of a list or linear data structure. Arrays are commonly declared with a fixed size. Because arrays occupy contiguous space, addition of elements beyond the predefined size may be difficult. Additional entries may conflict with existing data in the memory, so the array may need to be re-initialized to fit to a new memory location. An array may sometimes be categorized into static arrays (discussed in this article) and dynamic arrays (a form of implementation where elements may be dynamically added and removed without having to re-initialize or other fast algorithm). Both of these contexts are expected to allow for constant time (random) access.