Some key features of Haskell include :

1. Purely Functional : Haskell is based on the principles of functional programming, where programs are composed of pure functions that produce output based solely on their input without any side effects.

2. Static Typing : Haskell has a strong static type system that helps catch many errors at compile time. The type system is also inferred, meaning the compiler can often determine the types of expressions without explicit type annotations.

3. Lazy Evaluation : Haskell uses lazy evaluation, which means that expressions are only evaluated when their values are actually needed. This allows for more efficient use of resources and enables the creation of potentially infinite data structures.

4. Type Inference : Haskell has powerful type inference capabilities, which means that the compiler can often infer the types of expressions without explicit type annotations. This reduces the need for manual type declarations and makes the code more concise.

5. Higher-Order Functions : Haskell treats functions as first-class citizens, which means that functions can be passed as arguments to other functions, returned as results, and stored in data structures. This enables powerful abstractions and code reuse.

6. Pattern Matching : Haskell has a rich pattern matching syntax that allows for concise and expressive code. Pattern matching is used to destructure data and control flow based on the shape and contents of values.

7. Type Classes : Haskell uses type classes to define a set of behaviors that types can adhere to. Type classes provide a way to achieve ad-hoc polymorphism and enable overloading of functions based on different types.