Multiple Attribute Dependency. It's when your build requires more than 1 attribute to function correctly. Less of a problem in 4E since you can boost 2 attributes at once, but 3E only boosted 1 at a time so many classes wanted very high starting stats all around. Exists a bit still in 4E with star warlocks, dual implement wizards, and wisdom twf rangers.
Multiple Item Dependency is less of a problem because it'll only exist if you multiclass or grab both halves of the class build (battle laser cleric, melee and ranged ranger).