AIn the [[mathematics|mathematical]] discipline of [[matrix theory]], a '''block matrix''' or a '''partitioned matrix''' is a partition of a [[Matrix (mathematics)|matrix]] into rectangular smaller matrices called '''blocks'''. Looking at it another way, the matrix is written in terms of smaller matrices written side-by-side. A block matrix must conform to a consistent way of splitting up the rows, and the columns: we group the rows into some adjacent 'bunches', and the columns likewise. The partition is into the rectangles described by one bunch of adjacent rows crossing one bunch of adjacent columns. In other words, the matrix is split up by some horizontal and vertical lines that go all the way across.
