A thin, membranous skin, such as a pellicle.

The layer adjacent to the valve metal in an electrochemical valve, in which is located the high voltage drop when current flows in the direction of high impedance.

Plastic material, such as cellulose acetate or cellulose nitrate, coated with a light-sensitive emulsion, used to make negatives or transparencies in radiography or photography.

A flat section of material that is extremely thin in comparison to its other dimensions and has a nominal maximum thickness of 250 micrometers and a lower limit of thickness of about 25 micrometers. Also known as self-supported film.

A pathological opacity, as of the cornea.

Oxide coating on a metal.