Science and technlogy

• Bit decay, in computing
• Software decay, in computing
• Distance decay
  Distance decay
  Distance decay is a geographical term which describes the effect of distance on cultural or spatial interactions. The distance decay effect states that the interaction between two locales declines as the distance between them increases...
  
  , in geography
• Exponential decay, the decrease of a value in proportion to its value
• Decay time (fall time), in electronics
• Network decay (channel drift), in television programming
• In music, how quickly the sound drops to the sustain level after the initial peak, see ADSR envelope

Biology

• Bacterial decay
  Decomposition
  Decomposition is the process by which organic material is broken down into simpler forms of matter. The process is essential for recycling the finite matter that occupies physical space in the biome. Bodies of living organisms begin to decompose shortly after death...
  
  , decomposition of organic matter
• Tooth decay (dental caries), in dentistry
• Mitochondrial decay
  Mitochondrial decay
  Mitochondrial decay is one major cause of aging, leading to the subsequent death in humans. The mitochondria are the power producing organelles found in every cell of every organ. Their primary function is to generate ATP through various energy cycles that involve nutrients and vitamins. ATP is...
  
  , in genetics

Physics

• Orbital decay
  Orbital decay
  Orbital decay is the process of prolonged reduction in the altitude of a satellite's orbit.This can be due to drag produced by an atmosphere due to frequent collisions between the satellite and surrounding air molecules. The drag experienced by the object is larger in the case of increased solar...
  
  , the process of prolonged reduction in the height of a satellite's orbit
• Particle decay
  Particle decay
  Particle decay is the spontaneous process of one elementary particle transforming into other elementary particles. During this process, an elementary particle becomes a different particle with less mass and an intermediate particle such as W boson in muon decay. The intermediate particle then...
  
  
• Radioactive decay
  Radioactive decay
  Radioactive decay is the process by which an atomic nucleus of an unstable atom loses energy by emitting ionizing particles . The emission is spontaneous, in that the atom decays without any physical interaction with another particle from outside the atom...
  
  
• Optical decay
  Optical decay
  Optical decay is process of relaxation of excitation of an excited quantum system, usually due to the spontaneous emission of a photon or a phonon.Optical decay is dominant mechanism of quenching of excitation of active optical media...
  
  , in quantum physics

Psychology and sociology

• Decay theory
  Decay theory
  Decay theory proposes that memory fades due to the mere passage of time. Information is therefore less available for later retrieval as time passes and memory, as well as memory strength, wears away. When we learn something new, a neurochemical “memory trace” is created. However, over time this...
  
  , in psychology and memory
• Social decay (decadence), in sociology
• Urban decay
  Urban decay
  Urban decay is the process whereby a previously functioning city, or part of a city, falls into disrepair and decrepitude...
  
  , in sociology

Entertainment

• Decay (DC Comics)
  Decay (DC Comics)
  Decay is a fictional character owned by DC Comics. She appears as a villain in the Wonder Woman comic book series.-Fictional character biography:...
  
  , a comic book character
• Decay Music
  Decay Music
  Decay Music is the 1976 debut album by Michael Nyman, released on Brian Eno's Obscure Records music label. The two works on the album, 1-100 and Bell Set No. 1 are both built around the musical concept of decay. Both of these experiment with percussive, long decay musical forms. 1-100 is...
  
  , 1976 music album by Michael Nyman
• Half-Life: Decay
  Half-Life: Decay
  Half-Life: Decay is an expansion pack for Valve Software's science fiction, first-person shooter video game Half-Life. Developed by Gearbox Software and published by Sierra Entertainment, Decay was released as part of the PlayStation 2 version of Half-Life released on November 14, 2001...
  
  , a computer game add-on
• Deekay
  DEEKAY
  DEEKAY is a Danish production/songwriting team founded by Lars Halvor Jensen, Martin Michael Larsson with other members The Flash, Obi and Josh. The name Deekay comes from the acronym dk, which means Denmark...
  
  , a danish production team