A groundnut is a peanut: the small brown nut people eat, and also the plant it grows on. The name is almost a little joke of nature. The plant flowers above the soil, then pushes the nuts down into the earth to finish growing, so people called them nuts of the ground. In American English you will nearly always hear peanut; groundnut can sound old, farm-like, or like English from another country. In Britain, and in much of Africa and South Asia, groundnut is still a normal word, especially on oil bottles and in farming. Though actually, a few other plants with nuts under the soil also get called groundnut in some places, but in learner English this word means the peanut you already know.

花生（農事上也說落花生）