Optical (adjective)

1. Relating to the science of optics or the properties of light.
2. Relating to the eyes or vision.
3. Involving or using light.
4. Relating to visible light as opposed to ultraviolet or infrared radiation.
5. Relating to the appearance or behavior of light.

Origin:

From greek 'optikos', relating to sight or vision.

Examples:

1. The telescope uses optical lenses to magnify distant objects.
2. An optical illusion can deceive the eye into seeing something that isn't there.
3. An optical mouse uses a light-emitting diode and photodiodes to detect movement.
4. UV rays and X-rays are not part of the optical spectrum.
5. The optical properties of a gemstone determine its brilliance and fire.