Membrane (noun)

1. A thin, pliable layer of tissue covering a surface or separating a space.
2. A synthetic material designed to act as a selective barrier, allowing certain substances to pass while blocking others.

Origin:

From middle french 'membrane' and latin 'membrana' meaning 'parchment', ultimately from the proto-indo-european root '*membra-' meaning 'skin, flesh'.

Examples:

1. The alveoli in our lungs are lined with a membrane that helps oxygen and carbon dioxide diffuse in and out of the bloodstream.
2. The tympanic membrane, also known as the eardrum, vibrates in response to sound waves and helps transmit them to the inner ear.
3. The cell membrane, composed of phospholipids and proteins, regulates the movement of substances in and out of the cell.
4. The dialysis machine uses a semipermeable membrane to filter waste products out of the blood.
5. A Gore-Tex jacket has a membrane that allows water vapor to escape while keeping rain out.