Paraquat is a chemical used by farmers to kill weeds. It works very fast — it burns the green parts of a plant on contact — and it is extremely poisonous to people. Even a small swallowed amount can destroy the lungs, and there is no antidote; this is why it has appeared so often in news stories about poisonings and suicides across Asia. Many countries have now banned it or restricted it tightly for that reason. The word is a trade name that became the ordinary name for the chemical, the way people say the brand and mean the substance. You will meet it in agricultural writing, in news reports, and in medical writing about poisoning. It is uncountable: 'paraquat', never 'a paraquat'. A note for readers in Taiwan: paraquat was a very familiar word here for decades, and the government banned its sale for farm use in 2019 after a long public debate about exactly these poisoning deaths. So it is one of those words that older Taiwanese people know immediately and younger ones may not.

巴拉刈（除草劑，台灣 2019 年起禁用；老一輩幾乎都聽過這個名字）。中國大陸多寫作「百草枯」。