Pentaerythritol tetranitrate (PETN), also known as PENT, PENTA, TEN, corpent, penthrite (or—rarely and primarily in German—as nitropenta), is the nitrate ester of pentaerythritol, and is structurally very similar to nitroglycerin. Penta refers to the five carbon atoms of the neopentane skeleton. PETN is best known as an explosive . It is one of the most powerful high explosives known, with a relative effectiveness factor of 1.66. PETN mixed with a plasticizer forms a plastic explosive. As a mixture with RDX and other minor additives, it forms another plastic explosive called Semtex.