The Full Form of 24D is 2,4–dichlorophenoxyacetic acid.

2,4-Dichlorophenoxyacetic acid is an organic compound with the chemical formula C₈H₆Cl₂O₃ which is usually referred to by its ISO common name 2,4-D. It is a systemic herbicide which selectively kills most broadleaf weeds by causing uncontrolled growth in them but most grasses such as cereals, lawn turf, and grassland are relatively unaffected.

2,4-D is one of the oldest and most widely available herbicides and defoliants in the world, having been commercially available since 1945, and is now produced by many chemical companies since the patent on it has long since expired. It can be found in numerous commercial lawn herbicide mixtures, and is widely used as a weedkiller on cereal crops, pastures, and orchards. Over 1,500 herbicide products contain 2,4-D as an active ingredient.