ETYM Latin de from + cadere to fall.
1. To fall into decay or ruin; SYN. crumble, delapidate.
2. To undergo decay or decomposition.

A decrease in the amplitude of a signal over time.
1. A gradual decrease; as of stored charge or current; SYN. decline.
2. An inferior state resulting from the process of decaying.
3. The organic phenomenon of rotting; SYN. decomposition.
4. The phenomenon of spontaneous changes in the nucleus of an atom; SYN. radioactive decay.
5. The process of gradually becoming inferior.
6. The spontaneous disintegration of a radioactive substance along with the emission of ionizing radiation; SYN. radioactive decay, disintegration.