Knowledge Engineering and Information Systems create structured frameworks that allow machines to reason about, manage, and apply complex human knowledge. Ontologies, taxonomies, and semantic networks encode domain expertise, enabling intelligent applications in medicine, law, engineering, and science. Knowledge graphs integrate heterogeneous data sources to reveal relationships across entities and concepts. AI enhances information retrieval, quality assessment, and contextual understanding. Interdisciplinary research involves computer science, linguistics, cognitive psychology, and domain specialists. Advanced reasoning systems support decision-making, problem-solving, and automation at scale. These technologies underpin natural language understanding, expert systems, enterprise knowledge management, and digital twins. Ethical considerations ensure accuracy, transparency, and responsible knowledge governance. Knowledge engineering empowers machines to operate as sophisticated collaborators in complex domains.