1. The branch of physics that deals with light and vision; primarily, the generation, propagation, and detection of electromagnetic radiation having wavelengths greater than x-rays and shorter than microwaves.
2. When referring to a singular noun, it means, the study of light or electromagnetic radiation in the visible, infrared, and ultraviolet regions.
3. As a plural noun, it refers to instruments used for detecting electromagnetic radiation and for attaining highly accurate long-range vision.

The science and technology of the interactions between sound waves and light waves passing through solid materials, especially as applied to the modulation and deflection of laser beams by ultrasonic waves which are important in laser and holographic technologies: Samuel Waters was intent on perfecting a system of acousto-optics to enable him to expand his holographic business which printed passes for the local bus system.

A branch of meteorological physics or physical meteorology in which phenomena are seen occurring in the sky and are described and explained: Atmospheric optics is the study of the optical characteristics of the atmosphere or products of atmospheric processes.

The term atmospheric optics is usually confined to visible and near visible radiation, however, unlike meteorological optics, it routinely includes temporal and spatial resolutions beyond those discernible with the naked eye.

"Meteorological optics" is that part of atmospheric optics concerned with the study of patterns observable with the naked eye.

This restriction is often relaxed slightly to allow the use of simple aids, such as binoculars or a polarizing filter.

Topics included in meteorological optics are sky color, mirages, rainbows, halos, glories, coronas, and shines.

1. The area of science devoted to the directing and guiding of electron beams using electric fields in the same manner as lenses are used on light beams.
2. The study of the motion of free electrons under the influence of electric and magnetic fields; as in laser technology, light amplificaion, and photoelectricity.
3. The science that deals with the direction, deflection, or focusing of beams of electrons by electric and magnetic fields; such as, in electron lenses.
4. The science of the control of electron motion by electron lenses in systems or under conditions analogous to those involving or affecting visible light.
5. A branch of electronics concerned with the behavior of the electron beam under the influence of electrostatic and electromagnetic forces.
6. The science of the emission and propagation of electrons and of the factors controlling and modifying their flow; especially, when applied to electron microscopy.
7. The science and technology concerned with the use of applied electrical fields to generate and to control optical radiation.

The term electron-optics is often used erroneously as a synonym for optoelectronic.

1. The study of the influence of an electric field on optical phenomena, as in the electro-optical Kerr effect (pattern of double refraction) and the Stark effect (effect of an electric field on spectrum lines).
2. A branch of physics that functions with the influence and effects of an electric field on light going through the optical properties of matter; especially, in its crystalline form.

These properties include the transmission, emission, and the absorption of light.

The term electro-optics is used interchangeably with the broader term optoelectronics.

A branch of optical technology dealing with systems that transmit light signals and images over short, and long, distances through the use of optical fibers (transparent, hair-thin strands of glass or plastic).

These fibers have a wide range of applications; such as, in the transmission of computer data, telephone messages, and other communications.