- A deterioration of condition.
- The process or result of being gradually decomposed.
- (intransitive, of organic material) To rot, to go bad.
"The cat's body decayed rapidly."
- (intransitive, aviation) Loss of airspeed due to drag.
- (intransitive) To deteriorate, to get worse, to lose strength or health, to decline in quality.
"The pair loved to take pictures in the decaying hospital on forty-third street."
- (intransitive, physics, of a satellite's orbit) To undergo prolonged reduction in altitude (above the orbited body).
"2009, Francis Lyall, Paul B. Larsen, Space Law: A Treatise, page 120:"
- (intransitive, transitive, physics, of a quantum system) To undergo optical decay, that is, to relax to a less excited state, usually by emitting a photon or phonon.
- (intransitive, computing, of software) To undergo software rot, that is, to fail to be updated in a changing environment,so as to eventually become legacy or obsolete.
- (intransitive, transitive, physics, chemistry, of an unstable atom) To change by undergoing fission, by emitting radiation, or by capturing or losing one or more electrons.
- (transitive) To cause to rot or deteriorate.
"The extreme humidity decayed the wooden sculptures in the museum's collection in a matter of years."
- (intransitive, electronics, of storage media or the data on them) To undergo bit rot, that is, gradual degradation.