Definicija: Obstojen organoklorov insekticid, znan tudi kot dikloro-difenil-trikloroetan, ki so ga razvili v štiridesetih letih dvajsetega stoletja in je bil na široko uporabljen zaradi svoje obstojnosti (to pomeni, da ga ni bilo potrebno ponovno uporabljati na istem območju), majhne škodljivosti za sesalce, preprostosti in nizke cene proizvodnje. V uporabo je prišel po vsem svetu in je ob drugih organoklorih imel pogubne posledice za vrste pri vrhu prehranjevalne verige, še zlasti na razmnoževanje določenih ujed. DDT je zelo obstojen, relativno netopen v vodi, a zelo topen v maščobah. Učinek na zdravje ljudi ni jasen, vendar je manj toksičen kot sorodne spojine. Strupen je za druge vretenčarje, zlasti ribe, kopiči se v maščobnem tkivu živali v obliki malo manj toksičnega DDE. Zaradi njegovega učinka na prostoživeče živali je danes njegova uporaba v večini držav prepovedana ali strogo omejena.

Definicija: A persistent organochlorine insecticide, also known as dichlorodiphenyltrichloroethane, that was introduced in the 1940s and used widely because of its persistence (meaning repeated applications were unnecessary), its low toxicity to mammals and its simplicity and cheapness of manufacture. It became dispersed all over the world and, with other organochlorines, had a disruptive effect on species high in food chains, especially on the breeding success of certain predatory birds. DDT is very stable, relatively insoluble in water, but highly soluble in fats. Health effects on humans are not clear, but it is less toxic than related compounds. It is poisonous to other vertebrates, especially fish, and is stored in the fatty tissue of animals as sublethal amounts of the less toxic DDE. Because of its effects on wildlife its use in most countries is now forbidden or strictly limited.