Memory Unit (MU): A unit of space available to the Runner to install programs. The Runner begins the game with four memory units.
Memory units (MU or ) are a special kind of resource in Android: Netrunner that place a constant restriction on how many programs the Runner can have installed at any given time. The Runner starts the game with 4MU, but this number can be increased or decreased by various cards and effects. Each program has a memory cost, which counts against the Runner's available MU. If the Runner ever has a combined total memory cost of programs greater than his/her available memory units, programs must be trashed.