Some number of tiers (servers, layers, elements, etc.). The term refers to the possibility of having different configurations; for example, two tiers may work for one situation, while 10 tiers are required for another. The "n" could be a larger number, depending on what the tiers refer to. For example, an "n-tier cluster" could refer to 12 CPUs (12 tiers) or even 500 CPUs (500 tiers). See two-tier client/server and three-tier client/server.