Because the Hebrew Bible describes the forbidden fruit only as peri, the term for general fruit, no one knows. It could be a fruit that doesn't exist anymore. Historians have speculated it may have been any one of these fruits: pomegranate, mango, fig, grape, etrog or citron, carob, pear, quince or mushroom.

But of the tree of the knowledge of good and evil, thou shalt not eat of it: for in the day that thou eatest thereof thou shalt surely die. As a metaphor outside of the Abrahamic religions, the phrase typically refers to any indulgence or pleasure that is considered illegal or immoral.

NLT It's only the fruit from the tree in the middle of the garden that we are not allowed to eat. God said, 'You must not eat it or even touch it; if you do, you will die. ''

Unlawful pleasure or enjoyment; illicit love. For example, After Mary moved in with John, Tom began courting her—forbidden fruit is sweet, I guess , or Smoking behind the woodshed, that's a case of forbidden fruit .