diff --git a/base/docs/basedocs.jl b/base/docs/basedocs.jl index dd4c8d64e7d4e..2ed1bd98caa5c 100644 --- a/base/docs/basedocs.jl +++ b/base/docs/basedocs.jl @@ -3185,14 +3185,27 @@ Any """ Union{} -`Union{}`, the empty [`Union`](@ref) of types, is the type that has no values. That is, it has the defining -property `isa(x, Union{}) == false` for any `x`. `Base.Bottom` is defined as its alias and the type of `Union{}` -is `Core.TypeofBottom`. +`Union{}`, the empty [`Union`](@ref) of types, is the *bottom* type of the type system. That is, for each +`T::Type`, `Union{} <: T`. Also see the subtyping operator's documentation: [`<:`](@ref). + +As such, `Union{}` is also an *empty*/*uninhabited* type, meaning that it has no values. That is, for each `x`, +`isa(x, Union{}) == false`. + +`Base.Bottom` is defined as its alias and the type of `Union{}` is `Core.TypeofBottom`. # Examples ```jldoctest julia> isa(nothing, Union{}) false + +julia> Union{} <: Int +true + +julia> typeof(Union{}) === Core.TypeofBottom +true + +julia> isa(Union{}, Union) +false ``` """ kw"Union{}", Base.Bottom