The
top type in the
type theory of
mathematics,
logic, and
computer science, commonly abbreviated as
top or by the
down tack symbol (⊤), is the
universal type, sometimes called the
universal supertype as all other types in any given type system are
subtypes of top. In most cases it is the type which contains every possible object in the type system of interest. It is in contrast with the
bottom type, or the
universal subtype, which every other type is supertype of and in most cases it is the type that contains no members at all.