It all depends on how different the new language from the languages you already know. Easy: To learn a language with the same paradigm as a language you know,

It all depends on how different the new language from the languages you already know. Easy: To learn a language with the same paradigm as a language you know, e.g. JS -> Python (both are procedural and dynamic); Java -> C# (both are procedural and static) Medium: To go from dynamic to static typing, e.g. Python (dynamic) -> Java (static) Hard: A new language that requires learning many new concepts unfamiliar to you before, e.g. Java/C# (with GC) -> Rust (no GC, borrow checker, RAII); Java (eager, OOP) -> Haskell (lazy, functional) Super hard: A new language that hardly has anything in common with languages you know, e.g. SQL (query language) -> Rust (systems programming language); Python (procedural, functional) -> Prolog (logic)