Definition
The general formulation of covariance and contravariance refers to how the components of a coordinate vector transform under a change of basis (passive transformation). Thus let V be a vector space of dimension n over the field of scalars S, and let each of f = (X1,...,Xn) and f' = (Y1,...,Yn) be a basis of V. Also, let the change of basis from f to f′ be given by
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(1)
for some invertible n×n matrix A with entries . Here, each vector Yj of the f' basis is a linear combination of the vectors Xi of the f basis, so that
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