Science / Chemistry / Semipermeable Membrane: A membrane that allows some but not all of the components in a mixture to pass through it. Semipermeable membranes are used in dialysis. MORE
Science / Biology / Selectively Permeable: Term describing a barrier that allows some chemicals to pass but not others. The cell membrane is such a barrier. MORE
Science / Geology / Impermeable Layer: A layer of rock, sediment or soil that does not allow water to pass through. This could be caused by a lack of pore space or pore spaces that are so small that water molecules have difficulty passing MORE
Health / Disease / Reservoir: (or Natural Reservoir)The long-term host of the pathogen of an infectious disease. The long term host may not get the disease carried by the pathogen or it may be asymptomatic and non-lethal. Examples MORE