A directed-energy weapon (DEW) emits energy

Energy

In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...

 in an aimed direction without the means of a projectile

Projectile

A projectile is any object projected into space by the exertion of a force. Although a thrown baseball is technically a projectile too, the term more commonly refers to a weapon....

. It transfers energy to a target for a desired effect. Intended effects may be non-lethal or lethal. Some such weapons are real, or are under active research and development

Research and development

The phrase research and development , according to the Organization for Economic Co-operation and Development, refers to "creative work undertaken on a systematic basis in order to increase the stock of knowledge, including knowledge of man, culture and society, and the use of this stock of...

.

The energy can come in various forms:

• Electromagnetic radiation
  Electromagnetic spectrum
  The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. The "electromagnetic spectrum" of an object is the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object....
  
  , in laser
  Laser
  A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
  
  s or maser
  Maser
  A maser is a device that produces coherent electromagnetic waves through amplification by stimulated emission. Historically, “maser” derives from the original, upper-case acronym MASER, which stands for "Microwave Amplification by Stimulated Emission of Radiation"...
  
  s
  • Heat
    Heat
    In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
    
    
• Particles with mass
  Mass
  Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...
  
  , in particle beam weapon
  Particle beam weapon
  A particle beam weapon uses an ultra-high-energy beam of atoms or electrons to damage a material target by hitting it, and thus disrupting its atomic and molecular structure. A particle beam weapon is a type of directed-energy weapon, which directs energy in a particular direction by a means of...
  
  s
• Flamethrowers
• Sound
  Sound
  Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...
  
  , in sonic weapons

Some such weapons, perhaps most, at present only appear in science fiction

Science fiction

Science fiction is a genre of fiction dealing with imaginary but more or less plausible content such as future settings, futuristic science and technology, space travel, aliens, and paranormal abilities...

, non-functional toy

Toy

A toy is any object that can be used for play. Toys are associated commonly with children and pets. Playing with toys is often thought to be an enjoyable means of training the young for life in human society. Different materials are used to make toys enjoyable and cuddly to both young and old...

s, film props

Theatrical property

A theatrical property, commonly referred to as a prop, is an object used on stage by actors to further the plot or story line of a theatrical production. Smaller props are referred to as "hand props". Larger props may also be set decoration, such as a chair or table. The difference between a set...

 or animation

Animation

Animation is the rapid display of a sequence of images of 2-D or 3-D artwork or model positions in order to create an illusion of movement. The effect is an optical illusion of motion due to the phenomenon of persistence of vision, and can be created and demonstrated in several ways...

.

In science fiction, these weapons are sometimes known as death rays or raygun

Raygun

Rayguns are a type of fictional directed-energy weapon. They have various alternate names: ray gun, death ray, beam gun, blaster, laser gun, phaser, etc. They are a well-known feature of science fiction; for such stories they typically have the general function of guns...

s and are usually portrayed as projecting energy at a person or object to kill or destroy.