1. The usually round, red or yellow, edible fruit of a small tree, Malus sylvestrius, of the rose family
2. The tree that produces such fruit
There are two words in Indo-European languages that originated as generic words for fruit. One is PIE *ab(e)l and the other is Greek melon (based on PIE mahla-, meaning "grapevine, branch"). Both of which contribute to the modern belief that the forbidden fruit Adam and Eve ate in Eden was an apple. This is highly unlikely, though, because apples did not exist in the area where Eden is believed to have been during biblical times.
Fun fact: Calling women's breasts melons goes all the way back to ancient Greek.