A semipermeable membrane, also termed a selectively permeable membrane, a partially permeable membrane or a differentially permeable membrane, is a membrane which will allow certain molecules or ions to pass through it by diffusion and occasionally specialized "facilitated diffusion". The rate of passage depends on the pressure, concentration and temperature of the molecules or solutes on either side, as well as the permeability of the membrane to each solute.Depending on the membrane and the solute, permeability may depend on solute size, solubility, properties, or chemistry. An example of a semi-permeable membrane is a lipid bilayer, on which is based the plasma membrane that surrounds all biological cells. Many natural and synthetic materials thicker than a membrane are also semipermeable. An example of this is the thin film on the inside of an egg
disapproval If you say that someone has a selective memory, you disapprove of the fact that they remember certain facts about something and deliberately forget others, often because it is convenient for them to do so. We seem to have a selective memory for the best bits of the past + selectively se·lec·tive·ly a tendency to selectively forget all the adverse effects of the drug
A selective process applies only to a few things or people. Selective breeding may result in a greyhound running faster and seeing better than a wolf. + selectively se·lec·tive·ly Within the project, trees are selectively cut on a 25-year rotation. + selectivity se·lec·tiv·ity The soldiers specialized in going out in small groups, to kill with a very high degree of selectivity
tending to select; characterized by careful choice; "an exceptionally quick and selective reader"- John Mason Brown characterized by very careful or fastidious selection; "the school was very selective in its admissions
When someone is selective, they choose things carefully, for example the things that they buy or do. Sales still happen, but buyers are more selective + selectively se·lec·tive·ly people on small incomes who wanted to shop selectively