Tabu search (TS) is a solution methodology within the area of metaheuristics. While the methodology applies to optimization problems in general, most TS applications have been and continue to be in discrete optimization. A key and distinguishing feature of tabu search is the use of special strategies based on adaptive memory. The underlying philosophy is that an effective search for optimal solutions should involve a flexible process that responds to the objective function landscape in a manner that allows it to learn appropriate directions to exploit specific areas of the solution space and useful departures to explore new terrain. The adaptive memory structures of tabu search enable the implementation of procedures that are capable of searching effectively and produce solutions of suitable quality within reasonable computational effort.