Conductivity and resistivity are inversely proportional, meaning as one increases, the other decreases. The discussion clarifies that while density may influence conductivity through atomic concentration, it does not directly determine it. The relationship between conductivity and density is complex and not straightforward, as different metals can have the same density but vastly different conductivities. The original claim from the book about conductance depending on density may be a misinterpretation or mistranslation. Overall, the key takeaway is that conductivity and resistivity are fundamentally defined in relation to each other, independent of density.