What Tree has round green fruit not apples?

There are many trees that have round green fruit that aren't apples! To give you a more accurate answer, I need some more information.

Can you tell me:

* Where do you live? The type of fruit trees common in a particular region can help narrow down the possibilities.

* What is the size of the fruit? Is it small like a grape, medium like a lime, or large like a grapefruit?

* What does the fruit taste like? Is it sweet, sour, or something else?

* What does the tree look like? What kind of leaves does it have? What does the bark look like?

With more information, I can help you identify the tree!