Metric space but where the distance between two distinct points can be zero.
Notable example: Minkowski space.
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A **pseudometric space** is a generalization of a metric space. In a metric space, the distance between two points must satisfy certain properties, including the identity of indiscernibles, which states that the distance between two distinct points must be positive. However, a pseudometric space relaxes this requirement. Formally, a pseudometric space is defined as a pair \((X, d)\), where: - \(X\) is a set.