Operand reuse
Beginner
Using a number many times after fetching it once, instead of fetching it again each time.
Novice
How many operations use each value read from a given level of memory. In a matrix multiplication every input value is needed many times, so a design that keeps it nearby saves memory traffic.
Expert
Measured per level of the hierarchy (DRAM, buffer, array, register). In an weight-stationary array each activation is reused times on its way across and each weight once per streamed row. Reuse is bounded by the algorithm and the capacity of each level.
Explained in Systolic arrays (Architectures).
See also: Arithmetic (operational) intensity.