"in" the island? "on" the island?

Q. How do we know when to use in and on?

"in" the island? "on" the island?

Answer:

IN Use in when something is located inside of a defined space. It could be a flat space, like a yard, or a three-dimensional space, like a box, house, or car. The space does not need to be closed on all sides (“There is water IN the glass”).

ON Use on when something is touching the surface of something. It could be a horizontal surface, like a floor or beach, or a vertical surface, like a wall (“They hung pictures ON the wall”). We also use “on” for the surfaces of body parts (“He has a tattoo ON his arm”).

• He works on an island.
• She lives on the island.
• I am visiting on the island.

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"In" when referring to a place with a "proper" name or specific boundaries:
-In New York City
-In the Amazon jungle
-In California
-In the backyard

"On" when the place is simply geographical:
-On the beach

-On the East coast
-On the mountain
- On the island