Lightweight programming language
These programming languages have simple syntax and semantics, so they could be learned easily and in little time. Some of them (like Lisp, Forth, Tcl) are so simple to implement that they have many implementations (""dialects""). Compiled languages. BASIC. BASIC implementations like Tiny BASIC were designed to be lightweight so that they could run on the microcomputers of the 1980s, because of memory constraints. Forth. Forth is a stack-based concatenative imperative programming language using reverse polish notation. Toy languages. Brainfuck. Brainfuck is an extremely minimalist esoteric programming language. Scripting languages. Io. Io is a prototype-based  object-oriented scripting language. Lisp. Lisp-like languages are very simple to implement, so there are many lightweight implementations of it. There are some notable implementations: Derivatives of Lisp: Tcl. Tcl-like languages can be easily implemented because of its simple syntax. Tcl itself maybe not so lightweight, but there exists some, if not many, lightweight implementations of languages which have Tcl-like syntax. Embedded languages. ECMAScript. There are many embeddable implementation of ECMAScript like: Derivatives of ECMAScript: Lua. Lua is a small (C source is approx. 300 kB tarball, as of version 5.3.5), simple, fast, portable and embeddable scripting  language (with LuaJIT as a JIT compiler making it very fast). It can be embedded in many applications, like games, to provide runtime scripting capabilities. Wren. Wren is a small, fast, object-oriented scripting language.