Decomposition was the process by which organic substances were broken down into a simpler form of matter. Bodies of living organisms began to decompose soon after death.
In 2365, Colonel Stephen Richey's partially decomposed remains were discovered in a room at the hotel Royale on Theta VIII. Data found that Richey's remains had not undergone advanced decomposition 283 years after his death due to the sterile environment of the hotel. (TNG: "The Royale")
In 2368, Data noted with scientific detachedness that there was a twelve per cent decomposition of the bitanium in the neural pathway links of his own recently discovered head. (TNG: "Time's Arrow")
In an alternate quantum reality in 2370, Data noted the beginnings of cellular decomposition in Geordi La Forge's corpse. (TNG: "Parallels")
In 2373, Vel feared his sister Piri would rot in the Akritirian maximum security detention facility for the rest of her life because of her terrorist activities. (VOY: "The Chute")
In 2374, Dr. Julian Bashir contemptuously remarked upon Keevan's disregard for his men being left to rot on a Class M planet while Keevan himself was safe as a prisoner of war. (DS9: "Rocks and Shoals")
Some time later, Damar told Tora Ziyal that Gul Dukat should have left her to rot in the Breen prison camp where he found her. (DS9: "Favor the Bold")
In 2375, Morica Bilby's body was discovered in a river on New Sydney, partially decomposed by organic solvents in the water. (DS9: "Prodigal Daughter")
In 2376, Tom Paris facetiously described Mortimer Harren as "rotting away down on deck 15" aboard the USS Voyager. (VOY: "Good Shepherd")
Mezoti asked Neelix if the crew of the Salvoxia were decomposed when the ship was found after drifting through space for eighty years. (VOY: "The Haunting of Deck Twelve")