More formally, in continuum mechanics a body \(\mathcal B\) is a collection of elements which can be put into one-to-one correspondence with some region \(\mathcal R\) of Euclidean point space. An element \(p \in \mathcal B\) is called a particle (or material point). Thus, given a body \(\mathcal B\), there is necessarily a mapping \(\chi\) that takes particles \(p \in \mathcal B\) into their geometric locations \(y \in \mathcal R\) in three-dimensional Euclidean space:
\(y = \chi(p) \quad \textrm{where} \quad p \in \mathcal B, \mathbf{y} \in \mathcal R.\)
The mapping \(\chi\) is called a configuration of the body \(\mathcal B\); \(\mathbf y\) is the position occupied by the particle \(p\) in the configuration \(\chi\); and \(\mathcal R\) is the region occupied by the body in the configuration \(\chi\). Often, we write \(\mathcal R = \chi \left( \mathcal B \right)\).