superkey

a superkey of a relation schema $\text{[math]}$ is a set of attributes $\text{[math]}$ with the property that no two tuples $\text{[math]}$ and $\text{[math]}$ in any legal relation state $\text{[math]}$ of $\text{[math]}$ will have $\text{[math]}$ . a key $\text{[math]}$ is a superkey with the additional property that removal of any attribute from $\text{[math]}$ will cause $\text{[math]}$ not to be a superkey anymore.
[cite:;from @elmasri_db_2015 chapter 14.3.3 definitions of keys and attributes participating in keys]