# Covariance and Contravariance

Rules for when a more specific or more general type can stand in for another.

## What is **Covariance and Contravariance**?

**Covariance** lets you use a more specific type than asked for where values come *out* (a list of `Cat`s can be read as a list of `Animal`s). **Contravariance** lets you use a more general type where values go *in* (an `Animal` handler can handle `Cat`s).

```csharp
IEnumerable<Cat> cats = new List<Cat>();
IEnumerable<Animal> animals = cats;      // covariance

Action<Animal> feed = a => a.Eat();
Action<Cat> feedCat = feed;              // contravariance
```

Level: Master · [More OOP terms at this level](https://www.ask-codey.com/glossary/subjects/oop/master)

Updated: September 27, 2026

Source: https://www.ask-codey.com/glossary/covariance-and-contravariance