A technology-critical element (TCE) is a chemical element that is critical to emerging technologies. Technology-critical elements are elements for which a striking acceleration in usage has emerged, relative to past consumption. Many advanced engineering applications, such as clean-energy production, communications and computing, use emergent technologies that utilize numerous chemical elements. The set of elements usually considered as TCEs vary depending on the source, but they usually include: Seventeen rare-earth elements Six platinum-group elements Twelve assorted elements