U

unary expression::An expression consisting of a single operand preceded or followed by a unary operator.

unary operator::An operator that takes a single operand. Unary operators in the C language are the complement operators (– ~ !), indirection operator (*), increment (++) and decrement (– –) operators, address-of operator (&), and sizeof operator. The unary plus (+) operator is legal but has no effect.

union::A set of values of different types that occupy the same storage space.