decay

[1]	decline , wane , ebb , dwindle , diminish , decrease
[2]	decline , waste away , atrophy , weaken , wither , degenerate , deteriorate , disintegrate , crumble
[3]	rot , decompose , moulder , putrefy , spoil , turn , go bad , go off
[4]	dilapidate

[1]	decline
[2]	decomposition
[3]	decline , weakening , failing , fading , deterioration , decadence , degeneration , wasting , atrophy , dilapidation , disintegration , collapse , downfall
[4]	rot , radioactive decay , disintegration , rotting , decomposition , mould , putrefaction , mortification