ammonium: the ion NH4 derived from ammonia; behaves in many respects like an alkali metal ion
binary compound: chemical compound composed of only two elements
parity bit: (computer science) a bit that is used in an error detection procedure in which a 0 or 1 is added to each group of bits so that it will have either an odd number of 1's or an even number of 1's; e.g., if the parity is odd then any group of bits that arrives with an even number of 1's must contain an error