A
property of a
physial item meaning how much
light can pass through it.
Transparent means almost all light goes through.
Translucent means only some light goes through.
Opaque means no light goes through.
Can be used for anything else that you can see through, whether physically or metaphorically.
Physical transparency is related to the number of unbonded electrons in the molecules of the substance. With more unbounded electrons, the material tends to absorb energy (in the form of photons), and then later release it at a different frequency, often in the infrared. So visible light is absorbed, and comes out as heat. Without those unbonded electrons, the energy is later released at the same frequency and in the same direction. So the material.