> For the complete documentation index, see [llms.txt](https://trizen.gitbook.io/sidef-lang/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://trizen.gitbook.io/sidef-lang/programming_tasks/i/inheritance/single.md).

# Single

```ruby
class Animal {}
class Dog << Animal {}
class Cat << Animal {}
class Lab << Dog {}
class Collie << Dog {}
```