Zero-Indexed

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Zero-indexed means the ordering starts at zero. A zero-indexed array starts counting positions from 0 instead of 1 so in the array ["a", "b", "c"], "a" is at index 0, "b" at index 1 and "c" at index 2.

Because developers know that arrays (list) count from zero, a common bug can occur from the requirement to “select the 3rd item in the list” where an API uses zero-indexed positions. This is another example of an assumption that technical development teams might make, which is likely to differ from users expectations of the system under test.
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