composed of many interconnected parts; compound; composite: a complex highway system. characterized by a very complicated or involved arrangement of parts, uni

composed of many interconnected parts; compound; composite: a complex highway system. characterized by a very complicated or involved arrangement of parts, units, etc.: complex machinery. I would say you could have a software system with many interconnected parts, and/or with a complicated or involved arrangement of parts, without having duplicate code or duplicated functionality.