2,4-Dichlorophenoxyacetic acid (usually called 2,4-D) is an organic compound with the chemical formula C8H6Cl2O3. 2,4-D is a chlorphenoxy herbicide that has been used to kill broadleaf weeds since the 1940s and is still one of the most commonly used herbicides in the world. It is a systemic herbicide which selectively kills most broadleaf weeds by causing uncontrolled growth in them, but leaves most grasses such as cereals, lawn turf, and grassland relatively unaffected.