Scala 3 is a major update to the Scala programming language. It aims to make the language more solid, learnable, and expressive. Changes include new type system features, simplifications to make code safer, restrictions on surprising behaviors, and an overhaul of metaprogramming capabilities.

Scala 3 implements many language changes and improvements over Scala 2. It strengthens Scala's foundations, makes the language easier and safer to use, and improves the consistency and expressiveness of language constructs. Key changes include intersection and union types, trait parameters, given instances, opaque type aliases, restricted implicit conversions, and a new metaprogramming model.