C# 14 introduces a new `extension` block syntax that goes beyond the classic extension methods limitation. Developers can now define extension properties, static members, and operators on types they don't own — all within a static class. The new syntax supports computed properties (no backing fields), static factory methods, and generic constraints. Old-style `this` parameter extensions remain fully supported and can coexist with the new syntax. This makes shared extension libraries significantly more expressive and natural to consume.