Lightweight programming language

Lightweight programming languages are designed to have small memory footprint, are easy to implement (important when porting a language to different systems), and/or have minimalist syntax and features.[1]

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").[2]

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.[3][4][5]

Embedded languages

ECMAScript

There are many embeddable implementation of ECMAScript like:

Duktape
Espruino
JerryScript
jsish
MuJS
QuickJS

Derivatives of ECMAScript:

Squirrel

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.[6]

Wren

Wren is a small, fast, object-oriented scripting language.[7]