decay(process or result of being gradually decomposed) noun [UK: dɪˈk.eɪ] [US: dəˈk.eɪ]
digestion [digestions](processing of decay in organic matter assisted by microorganisms) noun [UK: dɪ.ˈdʒes.tʃən] [US: daɪ.ˈdʒes.tʃən]
rot [rots](process of becoming rotten, see also: decay; putrefaction) noun [UK: rɒt] [US: ˈrɑːt]He could not by any means tolerate the ghastly smell of rotting onion. = Él no podía tolerar bajo ninguna circunstancia el espantoso olor de cebollas en putrefacción.