A plum is a fruit that belongs to the subgenus Prunus as well as the genus Prunus. This fruit comes in many species, and taxonomists cannot agree on how many exactly. Depending on who you are asking to, between 19 and 40 different species of plum currently exist. However, only two species, the hexaploid European plum (Prunus domestica) and the diploid Japanese plum (Prunus salicina and hybrids), play a significant, commercial role.
The plum is a drupe, so its firm and juicy flesh contains one single, hard seed. The plum is usually not too big (between 1-3 inch diameter) and its shape is globose or more oval. The plum’s skin is soft with a natural wax layer.