A unitary n × n {\displaystyle {}n\times n} -matrix M ∈ GL n ( C ) {\displaystyle {}M\in \operatorname {GL} _{n}\!{\left(\mathbb {C} \right)}} fulfilling
is called a special unitary matrix. The set of all special unitary matrices is called the special unitary group; it is denoted by SU n {\displaystyle {}\operatorname {SU} _{n}} .