Keyword Cannibalization
Cannibalization happens when several pages on the same site target the same keyword. They compete with each other instead of reinforcing one another.
Google has to pick which page to show for a given query. When two pages fight for the same term, authority gets diluted and neither ranks as well as a single, clear page would.
The fix: one primary keyword per page, a clear content architecture, and internal links pointing to the reference page instead of duplicating it.