# Is union abstract type?
**URL:** https://discourse.julialang.org/t/is-union-abstract-type/123782
**Category:** General Usage
**Created:** [December 12, 2024, 6:59pm UTC](https://discourse.julialang.org/t/is-union-abstract-type/123782 "2024-12-12T18:59:18Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@garazha-ilya](https://discourse.julialang.org/u/garazha-ilya)
#### Post date: [December 12, 2024, 6:59pm UTC](https://discourse.julialang.org/t/is-union-abstract-type/123782/1 "2024-12-12T18:59:18Z")
Despite the fact that the [documentation says](https://docs.julialang.org/en/v1/manual/types/#Type-Unions) that union is an abstract type, the `isabstracttype()` function returns false:
```julia
IntOrString = Union{Int,AbstractString}
isabstracttype(IntOrString)
```
```julia
false
```
---
### Author:  [@stevengj](https://discourse.julialang.org/u/stevengj)
#### Post date: [December 12, 2024, 7:02pm UTC](https://discourse.julialang.org/t/is-union-abstract-type/123782/2 "2024-12-12T19:02:26Z")
This is the documented behavior of `isabstracttype`:
> Determine whether type `T` was declared as an abstract type (i.e. using the `abstract type` syntax). Note that this is **not the negation** of `isconcretetype(T).` _[emphasis added]_
It sounds like you want `!isconcretetype`, e.g.
```julia
julia> !isconcretetype(IntOrString)
true
```
---
### Author:  [@garazha-ilya](https://discourse.julialang.org/u/garazha-ilya)
#### Post date: [December 12, 2024, 7:23pm UTC](https://discourse.julialang.org/t/is-union-abstract-type/123782/3 "2024-12-12T19:23:16Z")
Thank you! That’s exactly what I wanted!)
---
### Author:  [@nsajko](https://discourse.julialang.org/u/nsajko)
#### Post date: [December 12, 2024, 10:15pm UTC](https://discourse.julialang.org/t/is-union-abstract-type/123782/4 "2024-12-12T22:15:33Z")
Related doc issue:
>
>
> Sometimes when the docs say "abstract", it means a type declared with \`abstract …type\`. In other occasions, it refers to any type that's not concrete. For clarity and consistency, I propose that all instances of the latter usage be replaced, e.g., with "non-concrete".
>
> xref #48142
>
> Examples:
>
> \* The \[\`Union\`\](https://docs.julialang.org/en/v1.11-dev/base/base/#Core.Union) doc string says: "Like other abstract types"
> \* The \[\`Tuple\`\](https://docs.julialang.org/en/v1.11-dev/base/base/#Core.Tuple) doc string says: "\`Tuple{Any}\` is considered an abstract type"