Identical particles

Identical particles are particles that have the same type and properties, such as electrons or photons. They are indistinguishable in every measurable way, meaning no experiment can tell one apart from another of the same kind. This indistinguishability affects how their quantum states are described—leading to specific rules for combining their wave functions, which explain phenomena like quantum statistics. In essence, all particles of the same kind are truly interchangeable; their identity is defined only by their collective properties, not by individual labels.