The term 'prison unit' can refer to three different components of a prison system: cellblock (9 letters), WARD (4 letters), and CELL (4 letters). A cellblock is a large area within a prison that contains multiple cells, each of which is used to house one or more inmates. A WARD is a smaller unit within a prison, typically containing fewer cells than a cellblock. Finally, a CELL is the smallest unit within a prison, typically containing only one inmate.