Let X be a set of formulas closed under taking subformulas.

Let X be a set whose members are all non-empty.

Let X be a formula with a classical bivalent truth value.

Let X be a set with a partial order .

Let X be an infinite set given the particular point topology.

Let X be a set given the particular point topology.

Let X be a matrix that holds the data.

Let X be an ordered set in the order topology.

Let X be a topological space, and A a set.

Let X be a smooth quasi-projective scheme over a field.