bottom, depths, basis
When someone exhibits profundity, they display great intellectual depth and understanding; profundity can also be the depth or complexity of something.
An unfounded claim is not based upon evidence; instead, it is unproven or groundless.
A profound saying is one of deep understanding and is rich in meaning.
The fundamental parts of something are its most important and basic parts.
Differentiated vocabulary for your students is just a click away.