Definition:Logical Connective/Unary

Definition
A unary logical connective (or one-place connective) is a connective whose effect on its compound statement is determined by the truth value of one substatement.

In standard Aristotelian logic, there are four of these.

The only non-trivial is logical not, as shown on Unary Boolean Functions.

Some treatments do not consider unary connectives to be logical connectives as such, because they do not actually "connect" anything, but this is a trivial point which can serve only to confuse.