# Terminology In old terminology, [[one-form|one-forms]] were called *covectors* because they [[Basis Transformation|transform]] like the [[basis]] does, while [[vector|vectors]] are called *contravectors* because they transform contra (i.e. opposite) to the basis. **"Co-goes-low"** is a helpful mnemonic to remember where the indices go. # Special Relativity In special relativity, we call $v^\nu$ the contravariant components of the 4-vector $v$ and $v_\nu$ its covariant components (i.e. the components of its corresponding [[one-form|one-form/dual vector]].