2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/96839The distinction between proper and improper mixtures is a staple of the discussion of foundational questions in quantum mechanics. Here we note an analogous distinction in the context of the theory of entanglement. The terminology of `proper' versus `improper' separability is proposed to mark the distinction.10 pages, LaTex, uses amsmath, 2 .eps figures. v2 additional figure; and reference and footnote to Seevinck and Uffink (2001). To appear in International Journal of Quantum InformationQuantum Physicstext