What is d2 and d10 deuterated?

D2 and D10 refer to deuterated forms of hydrogen compounds. D2, also known as deuterium gas, consists of two deuterium atoms (heavy hydrogen) and is commonly used in various scientific applications, including nuclear magnetic resonance (NMR) spectroscopy. D10, on the other hand, typically refers to a fully deuterated compound where all hydrogen atoms are replaced by deuterium, such as deuterated octane (C8D18), which is used in research to study molecular structures and dynamics.