Reason, also known as ReasonML, is a general-purpose, high-level, multi-paradigm, functional and object-oriented programming language and syntax extension and toolchain for OCaml created by Jordan Walke, who also created the React framework, at Facebook.

[5] The Reason community officially provides ReasonReact as a solution for React-based web applications.

[8] BuckleScript was forked to Melange[9] to continue to support compiling OCaml to JavaScript.

While Reason compiles down to native code via OCaml's toolchain, it specifically differs in its syntax, error messaging, and editor tooling.

While OCaml often relies on Indentation and begin/end keywords, Reason tends to use curly braces to delimit blocks and semicolons for separation of expressions.