What is the definition permeability?

Semi-permeable means partially permeable. The term semi-permeable is composed of two Words -semi and permeable. Semi is prefix in Latin and means half, or incompletely or somewhat. Permeability refers to the quality of diffusion or seeping or penetrating. This quality is generally associated with liquids or gases. Thus, semi-permeable is used to describe something that allows the passage of some substances and blocks other or not required substances.