In Japanese, keiretsu (系列) means a system, series, or grouping of enterprises, referring to a network of interdependent companies linked by cross-shareholdings and close business relationships, essentially a business group that prioritizes mutual success, often centered around a main bank or trading company, and replacing the pre-WWII zaibatsu. These groups can be horizontal (banks and diverse firms) or vertical (manufacturer-supplier chains) and foster cooperation, though they were once seen as trade barriers.