Set Let a set be an unordered collection of elements Example: This is a set SSS S={3,5,1982549}S2={2n∣n=1,2,5}={2,4,10}\begin{gather*} S=\{3,5,1982549\}\\ S_2=\{2n\quad|\quad n=1,2,5\}=\{2,4,10\} \end{gather*}S={3,5,1982549}S2={2n∣n=1,2,5}={2,4,10} The means “such that”