I often hear people use “between” when they mean “among”.

Problem:
The preposition “between” should not be used when expressing a relationship for three or more items.

Explanation:
The preposition “between” means in the space separating (two people, objects, etc.) or intermediate to. The primary definition of the preposition “among” is in the midst of.

If you look up the origin of “between”, you see that the tw in “between” is related to the tw in “two”. You can use this as a mnemonic to remind you that you should use “between” when expressing a relationship for two items and therefore that you should use “among” otherwise (for three or more items).

Solution:
Use “between” when you’re talking about two items; use “among” when you’re talking about three or more items.