In strict usage, integrated circuit refers to the single-piece circuit construction originally known as a monolithic integrated circuit, built on a single piece of silicon.[2][3] In general usage, circuits not meeting this strict definition are sometimes referred to as ICs, which are constructed using many different technologies, e.g. 3D IC, 2.5D IC, MCM, thin-film transistors, thick-film technologies, or hybrid integrated circuits. The choice of terminology frequently appears in discussions related to whether Moore's Law is obsolete.