As you already know, this term is also worth taking a look at its Latin roots: “permeare” can be translated as “pass through” or “wander through” and so we are dealing with the liquid or filtered solution that is obtained at the end of a membrane process. By the way, the portion of liquid that cannot completely pass through filtration and is retained due to the solids it contains is called retentate. Do you still want to hear the underlying Latin term here? Very well, “retinere” means “back” or “hold on.”