We have seen that the essential feature of a vector is that, in any rectangular cartesian coordinate system, it may be represented by three components, each associated with a particular axis. These components depend only on the orientation of the axes and transform according to the rules (2.1) when the axes are rotated. Tensor analysis may be regarded as a generalization of vector analysis to certain mathematical and physical entities known as tensors which require more than three components for their complete specification. There are again physically meaningful rules for transforming the components of tensors when the axes are changed. To give some motivation for the study of tensors, we shall first provide a specific example.