Cycle detection prevents relationship loops from occurring. A relationship loop occurs when an item has both a forward and a backward relationship with another item within the same relationship hierarchy.

For example, if item 1 has a forward relationship with item 2, and you create a forward relationship from item 2 to item 1, you create a relationship loop.

In another example, if item 3 has a backward relationship to item 1 through item 2, creating a forward relationship from item 3 to item 1 creates a relationship loop.