Elementary-set-theory notation Share. Subset strict subset and superset. A set may be defined by a membership rule formula or by listing its members within braces.
Usually sets are represented in curly braces for example A 1234 is a set.
It says the set of all xs such that x is greater than 0. You never know when set notation is going to pop up. Also check the set symbols here. These elements could be numbers alphabets variables etc.