A Polish space is a topological space whose topology can be induced by a complete separable metric. The completeness requirement concerns some compatible metric; it need not hold for every metric inducing the topology. Euclidean spaces are examples.
Articles by others on the same topic
A Polish space is a concept from the field of topology and descriptive set theory. Specifically, a Polish space is a topological space that is separable (contains a countable dense subset) and completely metrizable (can be endowed with a metric that induces its topology and is complete, meaning every Cauchy sequence converges within the space).