# Definition talk:Matrix

$\mathbf M = \begin{bmatrix} \mathbf A & \mathbf B \\ \mathbf C & \mathbf D \end{bmatrix}$.
If you like, but it's probably not that important as the notation as used here is standard and understood to mean what we have described. Incidentally, is there any difference? Can it be argued that the brackets around the matrix are conceptual only and therefore do not have the same force of meaning as the brackets around a set? That is, $\left\{{A, B, C, D}\right\}$ where $A, B, C, D$ are sets is not the same as $\cup \left\{{A, B, C, D}\right\}$ which would be the conceptual analogue.